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  • WebSocket API 1.1 released!

    - by Pavel Bucek
    Its my please to announce that JSR 356 – Java API for WebSocket maintenance release ballot vote finished with majority of “yes” votes (actually, only one eligible voter did not vote, all other votes were “yeses”). New release is maintenance release and it addresses only one issue:  WEBSOCKET_SPEC-226. What changed in the 1.1? Version 1.1 is fully backwards compatible with version 1.0, there are only two methods added to javax.websocket.Session: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 /** * Register to handle to incoming messages in this conversation. A maximum of one message handler per * native websocket message type (text, binary, pong) may be added to each Session. I.e. a maximum * of one message handler to handle incoming text messages a maximum of one message handler for * handling incoming binary messages, and a maximum of one for handling incoming pong * messages. For further details of which message handlers handle which of the native websocket * message types please see {@link MessageHandler.Whole} and {@link MessageHandler.Partial}. * Adding more than one of any one type will result in a runtime exception. * * @param clazz   type of the message processed by message handler to be registered. * @param handler whole message handler to be added. * @throws IllegalStateException if there is already a MessageHandler registered for the same native *                               websocket message type as this handler. */ public void addMessageHandler(Class<T> clazz, MessageHandler.Whole<T> handler); /** * Register to handle to incoming messages in this conversation. A maximum of one message handler per * native websocket message type (text, binary, pong) may be added to each Session. I.e. a maximum * of one message handler to handle incoming text messages a maximum of one message handler for * handling incoming binary messages, and a maximum of one for handling incoming pong * messages. For further details of which message handlers handle which of the native websocket * message types please see {@link MessageHandler.Whole} and {@link MessageHandler.Partial}. * Adding more than one of any one type will result in a runtime exception. * * * @param clazz   type of the message processed by message handler to be registered. * @param handler partial message handler to be added. * @throws IllegalStateException if there is already a MessageHandler registered for the same native *                               websocket message type as this handler. */ public void addMessageHandler(Class<T> clazz, MessageHandler.Partial<T> handler); Why do we need to add those methods? Short and not precise version: to support Lambda expressions as MessageHandlers. Longer and slightly more precise explanation: old Session#addMessageHandler method (which is still there and works as it worked till now) does rely on getting the generic parameter during the runtime, which is not (always) possible. The unfortunate part is that it works for some common cases and the expert group did not catch this issue before 1.0 release because of that. The issue is really clearly visible when Lambdas are used as message handlers: 1 2 3 session.addMessageHandler(message -> { System.out.println("### Received: " + message); }); There is no way for the JSR 356 implementation to get the type of the used Lambda expression, thus this call will always result in an exception. Since all modern IDEs do recommend to use Lambda expressions when possible and MessageHandler interfaces are single method interfaces, it basically just scream “use Lambdas” all over the place but when you do that, the application will fail during runtime. Only solution we currently have is to explicitly provide the type of registered MessageHandler. (There might be another sometime in the future when generic type reification is introduced, but that is not going to happen soon enough). So the example above will then be: 1 2 3 session.addMessageHandler(String.class, message -> { System.out.println("### Received: " + message); }); and voila, it works. There are some limitations – you cannot do 1 List<String>.class , so you will need to encapsulate these types when you want to use them in MessageHandler implementation (something like “class MyType extends ArrayList<String>”). There is no better way how to solve this issue, because Java currently does not provide good way how to describe generic types. The api itself is available on maven central, look for javax.websocket:javax.websocket-api:1.1. The reference implementation is project Tyrus, which implements WebSocket API 1.1 from version 1.8.

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  • SQL SERVER – Weekly Series – Memory Lane – #004

    - by pinaldave
    Here is the list of curetted articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2006 Auto Generate Script to Delete Deprecated Fields in Current Database In early career everytime I have to drop a column, I had hard time doing it because I was scared what if that column was needed somewhere in the code. Due to this fear I never dropped any column. I just renamed the column. If the column which I renamed was needed afterwards it was very easy to rename it back again. However, it is not recommended to keep the deleted column renamed in the database. At every interval I used to drop the columns which was prefixed with specific word. This script is 6 years old but still works. Give it a look, I am open for improvements. 2007 Shrinking Truncate Log File – Log Full – Part 2 Shrinking database or mdf file is indeed bad thing and it creates lots of problems. However, once in a while there is legit requirement to shrink the log file – a very rare one. In the rare occasion shrinking or truncating the log file may be the only solution. However, one should make sure to take backup before and after the truncate or shrink as in case of a disaster they can be very useful. Remember that truncating log file will break the log chain and while restore it can create major issue. Anyway, use this feature with caution. 2008 Simple Use of Cursor to Print All Stored Procedures of Database Including Schema This is a very interesting requirement I used to face in my early career days, I needed to print all the Stored procedures of my database. Interesting enough I had written a cursor to do so. Today when I look back at this stored procedure, I believe there will be a much cleaner way to do the same task, however, I still use this SP quite often when I have to document all the stored procedures of my database. Interesting Observation about Order of Resultset without ORDER BY In industry many developers avoid using ORDER BY clause to display the result in particular order thinking that Index is enforcing the order. In this interesting example, I demonstrate that without using ORDER BY, same table and similar query can return different results. Query optimizer always returns results using any method which is optimized for performance. The learning is There is no order unless ORDER BY is used. 2009 Size of Index Table – A Puzzle to Find Index Size for Each Index on Table I asked this puzzle earlier where I asked how to find the Index size for each of the tables. The puzzle was very well received and lots of interesting answers were received. To answer this question I have written following blog posts. I suggest this weekend you try to solve this problem and see if you can come up with a better solution. If not, well here are the solutions. Solution 1 | Solution 2 | Solution 3 Understanding Table Hints with Examples Hints are options and strong suggestions specified for enforcement by the SQL Server query processor on DML statements. The hints override any execution plan the query optimizer might select for a query. The SQL Server Query optimizer is a very smart tool and it makes a better selection of execution plan. Suggesting hints to the Query Optimizer should be attempted when absolutely necessary and by experienced developers who know exactly what they are doing (or in development as a way to experiment and learn). Interesting Observation – TOP 100 PERCENT and ORDER BY I have seen developers and DBAs using TOP very causally when they have to use the ORDER BY clause. Theoretically, there is no need of ORDER BY in the view at all. All the ordering should be done outside the view and view should just have the SELECT statement in it. It was quite common that to save this extra typing by including ordering inside of the view. At several instances developers want a complete resultset and for the same they include TOP 100 PERCENT along with ORDER BY, assuming that this will simulate the SELECT statement with ORDER BY. 2010 SQLPASS Nov 8-11, 2010-Seattle – An Alternative Look at Experience In year 2010 I attended most prestigious SQL Server event SQLPASS between Nov 8-11, 2010 at Seattle. I have only one expression for the event - Best Summit Ever. Instead of writing about my usual routine or the event, I wrote about the interesting things I did and how I felt about it! When I go back and read it, I feel that this is the best event I attended in year 2010. Change Database Access to Single User Mode Using SSMS Image says all. 2011 SQL Server 2012 has introduced new analytic functions. These functions were long awaited and I am glad that they are now here. Before when any of this function was needed, people used to write long T-SQL code to simulate these functions. But now there’s no need of doing so. Having available native function also helps performance as well readability. Function SQLAuthority MSDN CUME_DIST CUME_DIST CUME_DIST FIRST_VALUE FIRST_VALUE FIRST_VALUE LAST_VALUE LAST_VALUE LAST_VALUE LEAD LEAD LEAD LAG LAG LAG PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_DISC PERCENTILE_DISC PERCENTILE_DISC PERCENT_RANK PERCENT_RANK PERCENT_RANK Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • CodePlex Daily Summary for Sunday, July 08, 2012

    CodePlex Daily Summary for Sunday, July 08, 2012Popular ReleasesBlackJumboDog: Ver5.6.7: 2012.07.08 Ver5.6.7 (1) ????????????????「????? Request.Receve()」?????????? (2) Web???????????FlMML customized: FlMML customized ??: FlMML customized ????。 ??、PCM??????????、??????。ecBlog: ecBlog 0.2: ecBlog alpha realaseTaskScheduler ASP.NET: Release 3 - 1.2.0.0: Release 3 - Version 1.2.0.0 That version was altered only the library: In TaskScheduler was added new properties: UseBackgroundThreads Enables the use of separate threads for each task. StoreThreadsInPool Manager enables to store in the Pool threads that are performing the tasks. OnStopSchedulerAutoCancelThreads Scheduler allows aborting threads when it is stopped. false if the scheduler is not aborted the threads that are running. AutoDeletedExecutedTasks Allows Manager Delete Task afte...DotNetNuke Persian Packages: ??? ?? ???? ????? ???? 6.2.0: *????? ???? ??? ?? ???? 6.2.0 ? ??????? ???? ????? ???? ??? ????? *????? ????? ????? ??? ??? ???? ??? ??????? ??????? - ???? *?????? ???? ??? ?????? ?? ???? ???? ????? ? ?? ??? ?? ???? ???? ?? *????? ????? ????? ????? ????? / ??????? ???? ?? ???? ??? ??? - ???? *???? ???? ???? ????? ? ??????? ??? ??? ??? ?? ???? *????? ????? ???????? ??? ? ??????? ?? ?? ?????? ????? ????????? ????? ?????? - ???? *????? ????? ?????? ????? ?? ???? ?? ?? ?? ???????? ????? ????? ????????? ????? ?????? *???? ?...testtom07052012git02: r1: r1Cypher Bot: Cypher Bot 4.1: Cypher Bot is the most advanced encryption tool on the planet.... and now it actually works. That's right we fixed the bugs! For a full program summary go to the Home Page or visit www.iRareMedia.com So what's new? We've pretty much fixed all the bugs, but here's a run down if you wanna know exactly what's different: Fixed Installation / Setup Error, where an error message would display: "No Internet Connection, Try Again Later" Fixed File Encryption / Decryption error where the file exten...Coding4Fun Kinect Service: Coding4Fun Kinect Service v1.5: Requires Kinect for Windows SDK v1.5 Minor bug fixes + Kinect for Windows SDK v1.5 Aligning version with the Kinect for Windows SDK requiredtedplay: tedplay 1.1: tedplay 1.1 source and Win32 binary is out now. Changes are: SID card support Commodore 64 PSID music format support optimized FIR filter global hotkeys for skipping tracks (Windows only) module properties window (Windows only) mutable noise channel via GUI button (Windows only) disable SID card from the menu (Windows only) bugfixes PSID tunes are played on the C64 clock frequency but in a Commodore plus/4 virtual machine. The purpose is not to have yet another SID player, but t...xUnit.net Contrib: xunitcontrib-resharper 0.6 (RS 7.0, 6.1.1): xunitcontrib release 0.6 (ReSharper runner) This release provides a test runner plugin for Resharper 7.0 (EAP build 82) and 6.1, targetting all versions of xUnit.net. (See the xUnit.net project to download xUnit.net itself.) Copies of the plugin that support previous verions of ReSharper can be downloaded from this release. The plan is to support the latest revisions of the last two paid-for major versions of ReSharper (namely 7.0 and 6.1) Also note that all builds work against ALL VERSIONS...Umbraco CMS: Umbraco 4.8.0 Beta: Whats newuComponents in the core Multi-Node Tree Picker, Multiple Textstring, Slider and XPath Lists Easier Lucene searching built in IFile providers for easier file handling Updated 3rd party libraries Applications / Trees moved out of the database SQL Azure support added Various bug fixes Getting Started A great place to start is with our Getting Started Guide: Getting Started Guide: http://umbraco.codeplex.com/Project/Download/FileDownload.aspx?DownloadId=197051 Make sure to...CODE Framework: 4.0.20704.0: See CODE Framework (.NET) Change Log for changes in this version.xUnit.net - Unit testing framework for C# and .NET (a successor to NUnit): xUnit.net 1.9.1: xUnit.net release 1.9.1Build #1600 Important note for Resharper users: Resharper support has been moved to the xUnit.net Contrib project. Important note for TestDriven.net users: If you are having issues running xUnit.net tests in TestDriven.net, especially on 64-bit Windows, we strongly recommend you upgrade to TD.NET version 3.0 or later. Important note for VS2012 users: The VS2012 runner is in the Visual Studio Gallery now, and should be installed via Tools | Extension Manager from insi...MVC Controls Toolkit: Mvc Controls Toolkit 2.2.0: Added Modified all Mv4 related features to conform with the Mvc4 RC Now all items controls accept any IEnumerable<T>(before just List<T> were accepted by most of controls) retrievalManager class that retrieves automatically data from a data source whenever it catchs events triggered by filtering, sorting, and paging controls move method to the updatesManager to move one child objects from a father to another. The move operation can be undone like the insert, update and delete operatio...IronPython: 2.7.3: On behalf of the IronPython team, I'm happy to announce the final release of IronPython 2.7.3. This release includes everything from IronPython 54498, 62475, and 74478 as well. Like all IronPython 2.7-series releases, .NET 4 is required to install it. Installing this release will replace any existing IronPython 2.7-series installation. The incompatibility with IronRuby has been resolved, and they can once again be installed side-by-side. The biggest improvements in IronPython 2.7.3 are: the...Mini SQL Query: Mini SQL Query (v1.0.68.441): Just a bug fix release for when the connections try to refresh after an edit. Make sure you read the Quickstart for an introduction.Microsoft Ajax Minifier: Microsoft Ajax Minifier 4.58: Fix for Issue #18296: provide "ALL" value to the -ignore switch to ignore all error and warning messages. Fix for issue #18293: if encountering EOF before a function declaration or expression is properly closed, throw an appropriate error and don't crash. Adjust the variable-renaming algorithm so it's very specific when renaming variables with the same number of references so a single source file ends up with the same minified names on different platforms. add the ability to specify kno...LogExpert: 1.4 build 4566: This release for the 1.4 version line contains various fixes which have been made some times ago. Until now these fixes were only available in the 1.5 alpha versions. It also contains a fix for: 710. Column finder (press F8 to show) Terminal server issues: Multiple sessions with same user should work now Settings Export/Import available via Settings Dialog still incomple (e.g. tab colors are not saved) maybe I change the file format one day no command line support yet (for importin...CommonLibrary.NET: CommonLibrary.NET 0.9.8.5 - Final Release: A collection of very reusable code and components in C# 4.0 ranging from ActiveRecord, Csv, Command Line Parsing, Configuration, Holiday Calendars, Logging, Authentication, and much more. FluentscriptCommonLibrary.NET 0.9.8 contains a scripting language called FluentScript. Releases notes for FluentScript located at http://fluentscript.codeplex.com/wikipage?action=Edit&title=Release%20Notes&referringTitle=Documentation Fluentscript - 0.9.8.5 - Final ReleaseApplication: FluentScript Versio...SharePoint 2010 Metro UI: SharePoint 2010 Metro UI8: Please review the documentation link for how to install. Installation takes some basic knowledge of how to upload and edit SharePoint Artifact files. Please view the discussions tab for ongoing FAQsNew ProjectsAdventures of Adventure Land: Adventures of Adventure Land is a new text based adventure. You will be able to level up, fight challenging enemies, use magical spells, and simply adventure.AdventureWorks Silverlight samples: AdventureWorks Silverlight samplesAFS.Collab.Duplex: my duplexarmmychan: ????????C# - WPF - .Net - MSSQL - Open Source Restaurant POS System: A C# .Net / WPF / MSSQL Restaurant Point of Sale (POS) Software that is PCI-DSS 2.0 Compliant running stable in many restaurants / integrated with MercuryPay.dcview: dcinside.com? ??? ? ?? ?? ??? ???? ???.DotNetNuke Contact Form: simple yet effective DotNetNuke contact formISBNdb.com Helper Library: A .net helper library that encapsulates all the functionality of the API at www.isbndb.com in .NET CLR objects.JPO Class Register: Simple class register.NACHA C# Class with WPF Test App: Do you need to generate a NACHA PPD file? This is great starting point for you! Actually, it's a great, almost finished, point for you! More info below.NotificationsWidget In ASP MVC: SummaryPayPal Manager: I decided to make a basic (for now) desktop client for PayPal to get better at WebRequests in VB.NET. I will be adding much more such as sending payments, etc.Pomodoro Timer Count Down App: Pomodoro count down timer Application Features ------------------------------- Pomodoro Mode Count down timer mode Start stop pause Notification Powershell HTML Highlight: Powershell html syntax highlightingProject F10_P1: F10 p1Razor-sharp your skills: This project will have details about the C# 2.0 C# 3.0 C# 4.0 C# 5.0 Salaria: Bienvenue sur notre projet "Salaria".SharePoint 2010 - Unlock SP Files: Unlock any file in SharePoint or get lock information of a SharePoint file.( Compatible with office 365) ""The file "" is locked for exclusive use by""SharePoint 2010 Metro Masterpage: This project will give you a full metro masterpage for sharepoint 2010SharePoint Cache Refresh Framework: This project's aim is build a small and easy to use framework for SharePoint developers to be able to control cached objects across servers in a SharePoint FarmTFSProjectTest: A test project.uhimania test project: testUpgrade SPSolution: This is a Sharepoint 2010 Management Shell cmdlet, which upgrades a sharepoint solution and installs/activates any new features added in the package.Video Frame Explorer: Video Frame Explorer allows you to make thumbnails (caps, previews) of video files. It supports of practically any videos-formats (even MP4, MKV, MOV if you havWML: WML

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  • Session Report - Modern Software Development Anti-Patterns

    - by Janice J. Heiss
    In this standing-room-only session, building upon his 2011 JavaOne Rock Star “Diabolical Developer” session, Martijn Verburg, this time along with Ben Evans, identified and explored common “anti-patterns” – ways of doing things that keep developers from doing their best work. They emphasized the importance of social interaction and team communication, along with identifying certain psychological pitfalls that lead developers astray. Their emphasis was less on technical coding errors and more how to function well and to keep one’s focus on what really matters. They are the authors of the highly regarded The Well-Grounded Java Developer and are both movers and shakers in the London JUG community and on the Java Community Process. The large room was packed as they gave a fast-moving, witty presentation with lots of laughs and personal anecdotes. Below are a few of the anti-patterns they discussed.Anti-Pattern One: Conference-Driven DeliveryThe theme here is the belief that “Real pros hack code and write their slides minutes before their talks.” Their response to this anti-pattern is an expression popular in the military – PPPPPP, which stands for, “Proper preparation prevents piss-poor performance.”“Communication is very important – probably more important than the code you write,” claimed Verburg. “The more you speak in front of large groups of people the easier it gets, but it’s always important to do dry runs, to present to smaller groups. And important to be members of user groups where you can give presentations. It’s a great place to practice speaking skills; to gain new skills; get new contacts, to network.”They encouraged attendees to record themselves and listen to themselves giving a presentation. They advised them to start with a spouse or friends if need be. Learning to communicate to a group, they argued, is essential to being a successful developer. The emphasis here is that software development is a team activity and good, clear, accessible communication is essential to the functioning of software teams. Anti-Pattern Two: Mortgage-Driven Development The main theme here was that, in a period of worldwide recession and economic stagnation, people are concerned about keeping their jobs. So there is a tendency for developers to treat knowledge as power and not share what they know about their systems with their colleagues, so when it comes time to fix a problem in production, they will be the only one who knows how to fix it – and will have made themselves an indispensable cog in a machine so you cannot be fired. So developers avoid documentation at all costs, or if documentation is required, put it on a USB chip and lock it in a lock box. As in the first anti-pattern, the idea here is that communicating well with your colleagues is essential and documentation is a key part of this. Social interactions are essential. Both Verburg and Evans insisted that increasingly, year by year, successful software development is more about communication than the technical aspects of the craft. Developers who understand this are the ones who will have the most success. Anti-Pattern Three: Distracted by Shiny – Always Use the Latest Technology to Stay AheadThe temptation here is to pick out some obscure framework, try a bit of Scala, HTML5, and Clojure, and always use the latest technology and upgrade to the latest point release of everything. Don’t worry if something works poorly because you are ahead of the curve. Verburg and Evans insisted that there need to be sound reasons for everything a developer does. Developers should not bring in something simply because for some reason they just feel like it or because it’s new. They recommended a site run by a developer named Matt Raible with excellent comparison spread sheets regarding Web frameworks and other apps. They praised it as a useful tool to help developers in their decision-making processes. They pointed out that good developers sometimes make bad choices out of boredom, to add shiny things to their CV, out of frustration with existing processes, or just from a lack of understanding. They pointed out that some code may stay in a business system for 15 or 20 years, but not all code is created equal and some may change after 3 or 6 months. Developers need to know where the code they are contributing fits in. What is its likely lifespan? Anti-Pattern Four: Design-Driven Design The anti-pattern: If you want to impress your colleagues and bosses, use design patents left, right, and center – MVC, Session Facades, SOA, etc. Or the UML modeling suite from IBM, back in the day… Generate super fast code. And the more jargon you can talk when in the vicinity of the manager the better.Verburg shared a true story about a time when he was interviewing a guy for a job and asked him what his previous work was. The interviewee said that he essentially took patterns and uses an approved book of Enterprise Architecture Patterns and applied them. Verburg was dumbstruck that someone could have a job in which they took patterns from a book and applied them. He pointed out that the idea that design is a separate activity is simply wrong. He repeated a saying that he uses, “You should pay your junior developers for the lines of code they write and the things they add; you should pay your senior developers for what they take away.”He explained that by encouraging people to take things away, the code base gets simpler and reflects the actual business use cases developers are trying to solve, as opposed to the framework that is being imposed. He told another true story about a project to decommission a very long system. 98% of the code was decommissioned and people got a nice bonus. But the 2% remained on the mainframe so the 98% reduction in code resulted in zero reduction in costs, because the entire mainframe was needed to run the 2% that was left. There is an incentive to get rid of source code and subsystems when they are no longer needed. The session continued with several more anti-patterns that were equally insightful.

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  • BizTalk: Sample: Context routing and Throttling with orchestration

    - by Leonid Ganeline
    The sample demonstrates using orchestration for throttling and using context routing. Usually throttling is implemented on the host level (in BizTalk 2010 we can also using the host instance level throttling). Here is demonstrated the throttling with orchestration convoy that slows down message flow from some customers. Sample implements sort of quality service agreement layer for different kind of customers. The sample demonstrates the context routing between orchestrations. It has several advantages over the content routing. For example, we don’t have to create the property schema and promote properties on the schemas; we don’t have to change the message content to change routing. Use case:  The BizTalk application has a main processing orchestration that process all input messages. The application usually works as an OLTP application. Input messages came in random order without peaks, typical scenario for the on-line users. But sometimes the big data batch payloads come. These batches overload processing orchestrations. All processes, activated by on-line users after the payload, come to the same queue and are processed only after the payload. Result is on-line users can see significant delay in processing. It can be minutes or hours, depending of the batch size. Requirements: On-line user’s processing should work without delays. Big batches cannot disturb on-line users. There should be higher priority for the on-line users and the lower priority for the batches. Design: Decision is to divide the message flow in two branches, one for on-line users and second for batches. Branch with batches provides messages to the processing line with low priority, and the on-line user’s branch – with high priority. All messages are provided by hi-speed receive port. BTS.ReceivePortName context property is used for routing. The Router orchestration separates messages sent from on-line users and from the batch messages. But the Router does not use the BizTalk provided value of this property, the Router set up this value by itself. Router uses the content of the messages to decide if it is from on-line users or from batches. The message context property the BTS.ReceivePortName is changed respectively, its value works as a recipient address, as the “To” address for the next recipient orchestrations. Those next orchestrations are the BatchBottleneck and the MainProcess orchestrations. Messages with context equal “ToBatch” are filtered up by the BatchBottleneck orchestration. It is a unified convoy orchestration and it throttles the message flow, delaying the message delivery to the MainProcess orchestration. The BatchBottleneck orchestration changes the message context to the “ToProcess” and sends messages one after another with small delay in between. Delay can be configured in the BizTalk config file as:                 <appSettings>                                 <add key="GLD_Tests_TwoWayRouting_BatchBottleneck_DelayMillisec" value="100"/>                 </appSettings>   Of course, messages with context equal “ToProcess” are filtered up by the MainProcess orchestration.   NOTES: Filters with string values: In Orchestrations (the first Receive shape in orchestration) use string values WITH quotes; in Send Ports use string values WITHOUT quotes. Filters on the Send Ports are dynamic; we can change them in run-time. Filters on the Orchestrations are static; we can change them only in design-time. To check the existence of the promoted property inside orchestration use the Expression shape with construction like this:       if (BTS.ReceivePortName exists myMessage) { …; } It is not possible in the Message Assignment shape because using the “if” statement inside Message Assignment is prohibited. Several predefined context properties can behave in specific way. Say MessageTracking.OriginatingMessage or XMLNORM.DocumentSpecName, they are required some internal rules should be applied to the format or usage of this properties. MessageTracking.* parameters require you have to use tracking and you can get unexpected run-time errors in some cases. My recommendation is - use very limited set of the predefined context properties. To “attach” the new promoted property to the message, we have to use correlation. The correlation type should include this property. [Here is a good explanation by Saravana ] The sample code is here [sorry, temporary trubles with CodePlex].

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  • C++/boost generator module, feedback/critic please

    - by aaa
    hello. I wrote this generator, and I think to submit to boost people. Can you give me some feedback about it it basically allows to collapse multidimensional loops to flat multi-index queue. Loop can be boost lambda expressions. Main reason for doing this is to make parallel loops easier and separate algorithm from controlling structure (my fieldwork is computational chemistry where deep loops are common) 1 #ifndef _GENERATOR_HPP_ 2 #define _GENERATOR_HPP_ 3 4 #include <boost/array.hpp> 5 #include <boost/lambda/lambda.hpp> 6 #include <boost/noncopyable.hpp> 7 8 #include <boost/mpl/bool.hpp> 9 #include <boost/mpl/int.hpp> 10 #include <boost/mpl/for_each.hpp> 11 #include <boost/mpl/range_c.hpp> 12 #include <boost/mpl/vector.hpp> 13 #include <boost/mpl/transform.hpp> 14 #include <boost/mpl/erase.hpp> 15 16 #include <boost/fusion/include/vector.hpp> 17 #include <boost/fusion/include/for_each.hpp> 18 #include <boost/fusion/include/at_c.hpp> 19 #include <boost/fusion/mpl.hpp> 20 #include <boost/fusion/include/as_vector.hpp> 21 22 #include <memory> 23 24 /** 25 for loop generator which can use lambda expressions. 26 27 For example: 28 @code 29 using namespace generator; 30 using namespace boost::lambda; 31 make_for(N, N, range(bind(std::max<int>, _1, _2), N), range(_2, _3+1)); 32 // equivalent to pseudocode 33 // for l=0,N: for k=0,N: for j=max(l,k),N: for i=k,j 34 @endcode 35 36 If range is given as upper bound only, 37 lower bound is assumed to be default constructed 38 Lambda placeholders may only reference first three indices. 39 */ 40 41 namespace generator { 42 namespace detail { 43 44 using boost::lambda::constant_type; 45 using boost::lambda::constant; 46 47 /// lambda expression identity 48 template<class E, class enable = void> 49 struct lambda { 50 typedef E type; 51 }; 52 53 /// transform/construct constant lambda expression from non-lambda 54 template<class E> 55 struct lambda<E, typename boost::disable_if< 56 boost::lambda::is_lambda_functor<E> >::type> 57 { 58 struct constant : boost::lambda::constant_type<E>::type { 59 typedef typename boost::lambda::constant_type<E>::type base_type; 60 constant() : base_type(boost::lambda::constant(E())) {} 61 constant(const E &e) : base_type(boost::lambda::constant(e)) {} 62 }; 63 typedef constant type; 64 }; 65 66 /// range functor 67 template<class L, class U> 68 struct range_ { 69 typedef boost::array<int,4> index_type; 70 range_(U upper) : bounds_(typename lambda<L>::type(), upper) {} 71 range_(L lower, U upper) : bounds_(lower, upper) {} 72 73 template< typename T, size_t N> 74 T lower(const boost::array<T,N> &index) { 75 return bound<0>(index); 76 } 77 78 template< typename T, size_t N> 79 T upper(const boost::array<T,N> &index) { 80 return bound<1>(index); 81 } 82 83 private: 84 template<bool b, typename T> 85 T bound(const boost::array<T,1> &index) { 86 return (boost::fusion::at_c<b>(bounds_))(index[0]); 87 } 88 89 template<bool b, typename T> 90 T bound(const boost::array<T,2> &index) { 91 return (boost::fusion::at_c<b>(bounds_))(index[0], index[1]); 92 } 93 94 template<bool b, typename T, size_t N> 95 T bound(const boost::array<T,N> &index) { 96 using boost::fusion::at_c; 97 return (at_c<b>(bounds_))(index[0], index[1], index[2]); 98 } 99 100 boost::fusion::vector<typename lambda<L>::type, 101 typename lambda<U>::type> bounds_; 102 }; 103 104 template<typename T, size_t N> 105 struct for_base { 106 typedef boost::array<T,N> value_type; 107 virtual ~for_base() {} 108 virtual value_type next() = 0; 109 }; 110 111 /// N-index generator 112 template<typename T, size_t N, class R, class I> 113 struct for_ : for_base<T,N> { 114 typedef typename for_base<T,N>::value_type value_type; 115 typedef R range_tuple; 116 for_(const range_tuple &r) : r_(r), state_(true) { 117 boost::fusion::for_each(r_, initialize(index)); 118 } 119 /// @return new generator 120 for_* new_() { return new for_(r_); } 121 /// @return next index value and increment 122 value_type next() { 123 value_type next; 124 using namespace boost::lambda; 125 typename value_type::iterator n = next.begin(); 126 typename value_type::iterator i = index.begin(); 127 boost::mpl::for_each<I>(*(var(n))++ = var(i)[_1]); 128 129 state_ = advance<N>(r_, index); 130 return next; 131 } 132 /// @return false if out of bounds, true otherwise 133 operator bool() { return state_; } 134 135 private: 136 /// initialize indices 137 struct initialize { 138 value_type &index_; 139 mutable size_t i_; 140 initialize(value_type &index) : index_(index), i_(0) {} 141 template<class R_> void operator()(R_& r) const { 142 index_[i_++] = r.lower(index_); 143 } 144 }; 145 146 /// advance index[0:M) 147 template<size_t M> 148 struct advance { 149 /// stop recursion 150 struct stop { 151 stop(R r, value_type &index) {} 152 }; 153 /// advance index 154 /// @param r range tuple 155 /// @param index index array 156 advance(R &r, value_type &index) : index_(index), i_(0) { 157 namespace fusion = boost::fusion; 158 index[M-1] += 1; // increment index 159 fusion::for_each(r, *this); // update indices 160 state_ = index[M-1] >= fusion::at_c<M-1>(r).upper(index); 161 if (state_) { // out of bounds 162 typename boost::mpl::if_c<(M > 1), 163 advance<M-1>, stop>::type(r, index); 164 } 165 } 166 /// apply lower bound of range to index 167 template<typename R_> void operator()(R_& r) const { 168 if (i_ >= M) index_[i_] = r.lower(index_); 169 ++i_; 170 } 171 /// @return false if out of bounds, true otherwise 172 operator bool() { return state_; } 173 private: 174 value_type &index_; ///< index array reference 175 mutable size_t i_; ///< running index 176 bool state_; ///< out of bounds state 177 }; 178 179 value_type index; 180 range_tuple r_; 181 bool state_; 182 }; 183 184 185 /// polymorphic generator template base 186 template<typename T,size_t N> 187 struct For : boost::noncopyable { 188 typedef boost::array<T,N> value_type; 189 /// @return next index value and increment 190 value_type next() { return for_->next(); } 191 /// @return false if out of bounds, true otherwise 192 operator bool() const { return for_; } 193 protected: 194 /// reset smart pointer 195 void reset(for_base<T,N> *f) { for_.reset(f); } 196 std::auto_ptr<for_base<T,N> > for_; 197 }; 198 199 /// range [T,R) type 200 template<typename T, typename R> 201 struct range_type { 202 typedef range_<T,R> type; 203 }; 204 205 /// range identity specialization 206 template<typename T, class L, class U> 207 struct range_type<T, range_<L,U> > { 208 typedef range_<L,U> type; 209 }; 210 211 namespace fusion = boost::fusion; 212 namespace mpl = boost::mpl; 213 214 template<typename T, size_t N, class R1, class R2, class R3, class R4> 215 struct range_tuple { 216 // full range vector 217 typedef typename mpl::vector<R1,R2,R3,R4> v; 218 typedef typename mpl::end<v>::type end; 219 typedef typename mpl::advance_c<typename mpl::begin<v>::type, N>::type pos; 220 // [0:N) range vector 221 typedef typename mpl::erase<v, pos, end>::type t; 222 // transform into proper range fusion::vector 223 typedef typename fusion::result_of::as_vector< 224 typename mpl::transform<t,range_type<T, mpl::_1> >::type 225 >::type type; 226 }; 227 228 229 template<typename T, size_t N, 230 class R1, class R2, class R3, class R4, 231 class O> 232 struct for_type { 233 typedef typename range_tuple<T,N,R1,R2,R3,R4>::type range_tuple; 234 typedef for_<T, N, range_tuple, O> type; 235 }; 236 237 } // namespace detail 238 239 240 /// default index order, [0:N) 241 template<size_t N> 242 struct order { 243 typedef boost::mpl::range_c<size_t,0, N> type; 244 }; 245 246 /// N-loop generator, 0 < N <= 5 247 /// @tparam T index type 248 /// @tparam N number of indices/loops 249 /// @tparam R1,... range types 250 /// @tparam O index order 251 template<typename T, size_t N, 252 class R1, class R2 = void, class R3 = void, class R4 = void, 253 class O = typename order<N>::type> 254 struct for_ : detail::for_type<T, N, R1, R2, R3, R4, O>::type { 255 typedef typename detail::for_type<T, N, R1, R2, R3, R4, O>::type base_type; 256 typedef typename base_type::range_tuple range_tuple; 257 for_(const range_tuple &range) : base_type(range) {} 258 }; 259 260 /// loop range [L:U) 261 /// @tparam L lower bound type 262 /// @tparam U upper bound type 263 /// @return range 264 template<class L, class U> 265 detail::range_<L,U> range(L lower, U upper) { 266 return detail::range_<L,U>(lower, upper); 267 } 268 269 /// make 4-loop generator with specified index ordering 270 template<typename T, class R1, class R2, class R3, class R4, class O> 271 for_<T, 4, R1, R2, R3, R4, O> 272 make_for(R1 r1, R2 r2, R3 r3, R4 r4, const O&) { 273 typedef for_<T, 4, R1, R2, R3, R4, O> F; 274 return F(F::range_tuple(r1, r2, r3, r4)); 275 } 276 277 /// polymorphic generator template forward declaration 278 template<typename T,size_t N> 279 struct For; 280 281 /// polymorphic 4-loop generator 282 template<typename T> 283 struct For<T,4> : detail::For<T,4> { 284 /// generator with default index ordering 285 template<class R1, class R2, class R3, class R4> 286 For(R1 r1, R2 r2, R3 r3, R4 r4) { 287 this->reset(make_for<T>(r1, r2, r3, r4).new_()); 288 } 289 /// generator with specified index ordering 290 template<class R1, class R2, class R3, class R4, class O> 291 For(R1 r1, R2 r2, R3 r3, R4 r4, O o) { 292 this->reset(make_for<T>(r1, r2, r3, r4, o).new_()); 293 } 294 }; 295 296 } 297 298 299 #endif /* _GENERATOR_HPP_ */

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  • Why is insertion into my tree faster on sorted input than random input?

    - by Juliet
    Now I've always heard binary search trees are faster to build from randomly selected data than ordered data, simply because ordered data requires explicit rebalancing to keep the tree height at a minimum. Recently I implemented an immutable treap, a special kind of binary search tree which uses randomization to keep itself relatively balanced. In contrast to what I expected, I found I can consistently build a treap about 2x faster and generally better balanced from ordered data than unordered data -- and I have no idea why. Here's my treap implementation: http://pastebin.com/VAfSJRwZ And here's a test program: using System; using System.Collections.Generic; using System.Linq; using System.Diagnostics; namespace ConsoleApplication1 { class Program { static Random rnd = new Random(); const int ITERATION_COUNT = 20; static void Main(string[] args) { List<double> rndTimes = new List<double>(); List<double> orderedTimes = new List<double>(); rndTimes.Add(TimeIt(50, RandomInsert)); rndTimes.Add(TimeIt(100, RandomInsert)); rndTimes.Add(TimeIt(200, RandomInsert)); rndTimes.Add(TimeIt(400, RandomInsert)); rndTimes.Add(TimeIt(800, RandomInsert)); rndTimes.Add(TimeIt(1000, RandomInsert)); rndTimes.Add(TimeIt(2000, RandomInsert)); rndTimes.Add(TimeIt(4000, RandomInsert)); rndTimes.Add(TimeIt(8000, RandomInsert)); rndTimes.Add(TimeIt(16000, RandomInsert)); rndTimes.Add(TimeIt(32000, RandomInsert)); rndTimes.Add(TimeIt(64000, RandomInsert)); rndTimes.Add(TimeIt(128000, RandomInsert)); string rndTimesAsString = string.Join("\n", rndTimes.Select(x => x.ToString()).ToArray()); orderedTimes.Add(TimeIt(50, OrderedInsert)); orderedTimes.Add(TimeIt(100, OrderedInsert)); orderedTimes.Add(TimeIt(200, OrderedInsert)); orderedTimes.Add(TimeIt(400, OrderedInsert)); orderedTimes.Add(TimeIt(800, OrderedInsert)); orderedTimes.Add(TimeIt(1000, OrderedInsert)); orderedTimes.Add(TimeIt(2000, OrderedInsert)); orderedTimes.Add(TimeIt(4000, OrderedInsert)); orderedTimes.Add(TimeIt(8000, OrderedInsert)); orderedTimes.Add(TimeIt(16000, OrderedInsert)); orderedTimes.Add(TimeIt(32000, OrderedInsert)); orderedTimes.Add(TimeIt(64000, OrderedInsert)); orderedTimes.Add(TimeIt(128000, OrderedInsert)); string orderedTimesAsString = string.Join("\n", orderedTimes.Select(x => x.ToString()).ToArray()); Console.WriteLine("Done"); } static double TimeIt(int insertCount, Action<int> f) { Console.WriteLine("TimeIt({0}, {1})", insertCount, f.Method.Name); List<double> times = new List<double>(); for (int i = 0; i < ITERATION_COUNT; i++) { Stopwatch sw = Stopwatch.StartNew(); f(insertCount); sw.Stop(); times.Add(sw.Elapsed.TotalMilliseconds); } return times.Average(); } static void RandomInsert(int insertCount) { Treap<double> tree = new Treap<double>((x, y) => x.CompareTo(y)); for (int i = 0; i < insertCount; i++) { tree = tree.Insert(rnd.NextDouble()); } } static void OrderedInsert(int insertCount) { Treap<double> tree = new Treap<double>((x, y) => x.CompareTo(y)); for(int i = 0; i < insertCount; i++) { tree = tree.Insert(i + rnd.NextDouble()); } } } } And here's a chart comparing random and ordered insertion times in milliseconds: Insertions Random Ordered RandomTime / OrderedTime 50 1.031665 0.261585 3.94 100 0.544345 1.377155 0.4 200 1.268320 0.734570 1.73 400 2.765555 1.639150 1.69 800 6.089700 3.558350 1.71 1000 7.855150 4.704190 1.67 2000 17.852000 12.554065 1.42 4000 40.157340 22.474445 1.79 8000 88.375430 48.364265 1.83 16000 197.524000 109.082200 1.81 32000 459.277050 238.154405 1.93 64000 1055.508875 512.020310 2.06 128000 2481.694230 1107.980425 2.24 I don't see anything in the code which makes ordered input asymptotically faster than unordered input, so I'm at a loss to explain the difference. Why is it so much faster to build a treap from ordered input than random input?

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  • Developing Schema Compare for Oracle (Part 4): Script Configuration

    - by Simon Cooper
    If you've had a chance to play around with the Schema Compare for Oracle beta, you may have come across this screen in the synchronization wizard: This screen is one of the few screens that, along with the project configuration form, doesn't come from SQL Compare. This screen was designed to solve a couple of issues that, although aren't specific to Oracle, are much more of a problem than on SQL Server: Datatype conversions and NOT NULL columns. 1. Datatype conversions SQL Server is generally quite forgiving when it comes to datatype conversions using ALTER TABLE. For example, you can convert from a VARCHAR to INT using ALTER TABLE as long as all the character values are parsable as integers. Oracle, on the other hand, only allows ALTER TABLE conversions that don't change the internal data format. Essentially, every change that requires an actual datatype conversion has to be done using a rebuild with a conversion function. That's OK, as we can simply hard-code the various conversion functions for the valid datatype conversions and insert those into the rebuild SELECT list. However, as there always is with Oracle, there's a catch. Have a look at the NUMTODSINTERVAL function. As well as specifying the value (or column) to convert, you have to specify an interval_unit, which tells oracle how to interpret the input number. We can't hardcode a default for this parameter, as it is entirely dependent on the user's data context! So, in order to convert NUMBER to INTERVAL DAY TO SECOND/INTERVAL YEAR TO MONTH, we need to have feedback from the user as to what to put in this parameter while we're generating the sync script - this requires a new step in the engine action/script generation to insert these values into the script, as well as new UI to allow the user to specify these values in a sensible fashion. In implementing the engine and UI infrastructure to allow this it made much more sense to implement it for any rebuild datatype conversion, not just NUMBER to INTERVALs. For conversions which we can do, we pre-fill the 'value' box with the appropriate function from the documentation. The user can also type in arbitary SQL expressions, which allows the user to specify optional format parameters for the relevant conversion functions, or indeed call their own functions to convert between values that don't have a built-in conversion defined. As the value gets inserted as-is into the rebuild SELECT list, any expression that is valid in that context can be specified as the conversion value. 2. NOT NULL columns Another problem that is solved by the new step in the sync wizard is adding a NOT NULL column to a table. If the table contains data (as most database tables do), you can't just add a NOT NULL column, as Oracle doesn't know what value to put in the new column for existing rows - the DDL statement will fail. There are actually 3 separate scenarios for this problem that have separate solutions within the engine: Adding a NOT NULL column to a table without a rebuild Here, the workaround is to add a column default with an appropriate value to the column you're adding: ALTER TABLE tbl1 ADD newcol NUMBER DEFAULT <value> NOT NULL; Note, however, there is something to bear in mind about this solution; once specified on a column, a default cannot be removed. To 'remove' a default from a column you change it to have a default of NULL, hence there's code in the engine to treat a NULL default the same as no default at all. Adding a NOT NULL column to a table, where a separate change forced a table rebuild Fortunately, in this case, a column default is not required - we can simply insert the default value into the rebuild SELECT clause. Changing an existing NULL to a NOT NULL column To implement this, we run an UPDATE command before the ALTER TABLE to change all the NULLs in the column to the required default value. For all three, we need some way of allowing the user to specify a default value to use instead of NULL; as this is essentially the same problem as datatype conversion (inserting values into the sync script), we can re-use the UI and engine implementation of datatype conversion values. We also provide the option to alter the new column to allow NULLs, or to ignore the problem completely. Note that there is the same (long-running) problem in SQL Compare, but it is much more of an issue in Oracle as you cannot easily roll back executed DDL statements if the script fails at some point during execution. Furthermore, the engine of SQL Compare is far less conducive to inserting user-supplied values into the generated script. As we're writing the Schema Compare engine from scratch, we used what we learnt from the SQL Compare engine and designed it to be far more modular, which makes inserting procedures like this much easier.

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  • Google and Bing Map APIs Compared

    - by SGWellens
    At one of the local golf courses I frequent, there is an open grass field next to the course. It is about eight acres in size and mowed regularly. It is permissible to hit golf balls there—you bring and shag our own balls. My golf colleagues and I spend hours there practicing, chatting and in general just wasting time. One of the guys brings Ginger, the amazing, incredible, wonder dog. Ginger is a Portuguese Pointer. She chases squirrels, begs for snacks and supervises us closely to make sure we don't misbehave.     Anyway, I decided to make a dedicated web page to measure distances on the field in yards using online mapping services. I started with Google maps and then did the same application with Bing maps. It is a good way to become familiar with the APIs. Here are images of the final two maps: Google:  Bing:   To start with online mapping services, you need to visit the respective websites and get a developers key. I pared the code down to the minimum to make it easier to compare the APIs. Google maps required this CSS (or it wouldn't work): <style type="text/css">     html     {         height: 100%;     }       body     {         height: 100%;         margin: 0;         padding: 0;     } Here is how the map scripts are included. Google requires the developer Key when loading the JavaScript, Bing requires it when the map object is created: Google: <script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?key=XXXXXXX&libraries=geometry&sensor=false" > </script> Bing: <script  type="text/javascript" src="http://ecn.dev.virtualearth.net/mapcontrol/mapcontrol.ashx?v=7.0"> </script> Note: I use jQuery to manipulate the DOM elements which may be overkill, but I may add more stuff to this application and I didn't want to have to add it later. Plus, I really like jQuery. Here is how the maps are created: Common Code (the same for both Google and Bing Maps):     <script type="text/javascript">         var gTheMap;         var gMarker1;         var gMarker2;           $(document).ready(DocLoaded);           function DocLoaded()         {             // golf course coordinates             var StartLat = 44.924254;             var StartLng = -93.366859;               // what element to display the map in             var mapdiv = $("#map_div")[0];   Google:         // where on earth the map should display         var StartPoint = new google.maps.LatLng(StartLat, StartLng);           // create the map         gTheMap = new google.maps.Map(mapdiv,             {                 center: StartPoint,                 zoom: 18,                 mapTypeId: google.maps.MapTypeId.SATELLITE             });           // place two markers         marker1 = PlaceMarker(new google.maps.LatLng(StartLat, StartLng + .0001));         marker2 = PlaceMarker(new google.maps.LatLng(StartLat, StartLng - .0001));           DragEnd(null);     } Bing:         // where on earth the map should display         var StartPoint = new  Microsoft.Maps.Location(StartLat, StartLng);           // create the map         gTheMap = new Microsoft.Maps.Map(mapdiv,             {                 credentials: 'Asbsa_hzfHl69XF3wxBd_WbW0dLNTRUH3ZHQG9qcV5EFRLuWEaOP1hjWdZ0A0P17',                 center: StartPoint,                 zoom: 18,                 mapTypeId: Microsoft.Maps.MapTypeId.aerial             });             // place two markers         marker1 = PlaceMarker(new Microsoft.Maps.Location(StartLat, StartLng + .0001));         marker2 = PlaceMarker(new Microsoft.Maps.Location(StartLat, StartLng - .0001));           DragEnd(null);     } Note: In the Bing documentation, mapTypeId: was missing from the list of options even though the sample code included it. Note: When creating the Bing map, use the developer Key for the credentials property. I immediately place two markers/pins on the map which is simpler that creating them on the fly with mouse clicks (as I first tried). The markers/pins are draggable and I capture the DragEnd event to calculate and display the distance in yards and draw a line when the user finishes dragging. Here is the code to place a marker: Google: // ---- PlaceMarker ------------------------------------   function PlaceMarker(location) {     var marker = new google.maps.Marker(         {             position: location,             map: gTheMap,             draggable: true         });     marker.addListener('dragend', DragEnd);     return marker; }   Bing: // ---- PlaceMarker ------------------------------------   function PlaceMarker(location) {     var marker = new Microsoft.Maps.Pushpin(location,     {         draggable : true     });     Microsoft.Maps.Events.addHandler(marker, 'dragend', DragEnd);     gTheMap.entities.push(marker);     return marker; } Here is the code than runs when the user stops dragging a marker: Google: // ---- DragEnd -------------------------------------------   var gLine = null;   function DragEnd(Event) {     var meters = google.maps.geometry.spherical.computeDistanceBetween(marker1.position, marker2.position);     var yards = meters * 1.0936133;     $("#message").text(yards.toFixed(1) + ' yards');    // draw a line connecting the points     var Endpoints = [marker1.position, marker2.position];       if (gLine == null)     {         gLine = new google.maps.Polyline({             path: Endpoints,             strokeColor: "#FFFF00",             strokeOpacity: 1.0,             strokeWeight: 2,             map: gTheMap         });     }     else        gLine.setPath(Endpoints); } Bing: // ---- DragEnd -------------------------------------------   var gLine = null;   function DragEnd(Args) {    var Distance =  CalculateDistance(marker1._location, marker2._location);      $("#message").text(Distance.toFixed(1) + ' yards');       // draw a line connecting the points    var Endpoints = [marker1._location, marker2._location];           if (gLine == null)    {        gLine = new Microsoft.Maps.Polyline(Endpoints,            {                strokeColor: new Microsoft.Maps.Color(0xFF, 0xFF, 0xFF, 0),  // aRGB                strokeThickness : 2            });          gTheMap.entities.push(gLine);    }    else        gLine.setLocations(Endpoints);  }   Note: I couldn't find a function to calculate the distance between points in the Bing API, so I wrote my own (CalculateDistance). If you want to see the source for it, you can pick it off the web page. Note: I was able to verify the accuracy of the measurements by using the golf hole next to the field. I put a pin/marker on the center of the green, and then by zooming in, I was able to see the 150 markers on the fairway and put the other pin/marker on one of them. Final Notes: All in all, the APIs are very similar. Both made it easy to accomplish a lot with a minimum amount of code. In one aerial view, there are leaves on the tree, in the other, the trees are bare. I don't know which service has the newer data. Here are links to working pages: Bing Map Demo Google Map Demo I hope someone finds this useful. Steve Wellens   CodeProject

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  • Google and Bing Map APIs Compared

    - by SGWellens
    At one of the local golf courses I frequent, there is an open grass field next to the course. It is about eight acres in size and mowed regularly. It is permissible to hit golf balls there—you bring and shag our own balls. My golf colleagues and I spend hours there practicing, chatting and in general just wasting time. One of the guys brings Ginger, the amazing, incredible, wonder dog. Ginger is a Hungarian Vizlas (or Hungarian pointer). She chases squirrels, begs for snacks and supervises us closely to make sure we don't misbehave. Anyway, I decided to make a dedicated web page to measure distances on the field in yards using online mapping services. I started with Google maps and then did the same application with Bing maps. It is a good way to become familiar with the APIs. Here are images of the final two maps: Google:  Bing:   To start with online mapping services, you need to visit the respective websites and get a developers key. I pared the code down to the minimum to make it easier to compare the APIs. Google maps required this CSS (or it wouldn't work): <style type="text/css">     html     {         height: 100%;     }       body     {         height: 100%;         margin: 0;         padding: 0;     } Here is how the map scripts are included. Google requires the developer Key when loading the JavaScript, Bing requires it when the map object is created: Google: <script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?key=XXXXXXX&libraries=geometry&sensor=false" > </script> Bing: <script  type="text/javascript" src="http://ecn.dev.virtualearth.net/mapcontrol/mapcontrol.ashx?v=7.0"> </script> Note: I use jQuery to manipulate the DOM elements which may be overkill, but I may add more stuff to this application and I didn't want to have to add it later. Plus, I really like jQuery. Here is how the maps are created: Common Code (the same for both Google and Bing Maps):     <script type="text/javascript">         var gTheMap;         var gMarker1;         var gMarker2;           $(document).ready(DocLoaded);           function DocLoaded()         {             // golf course coordinates             var StartLat = 44.924254;             var StartLng = -93.366859;               // what element to display the map in             var mapdiv = $("#map_div")[0];   Google:         // where on earth the map should display         var StartPoint = new google.maps.LatLng(StartLat, StartLng);           // create the map         gTheMap = new google.maps.Map(mapdiv,             {                 center: StartPoint,                 zoom: 18,                 mapTypeId: google.maps.MapTypeId.SATELLITE             });           // place two markers         marker1 = PlaceMarker(new google.maps.LatLng(StartLat, StartLng + .0001));         marker2 = PlaceMarker(new google.maps.LatLng(StartLat, StartLng - .0001));           DragEnd(null);     } Bing:         // where on earth the map should display         var StartPoint = new  Microsoft.Maps.Location(StartLat, StartLng);           // create the map         gTheMap = new Microsoft.Maps.Map(mapdiv,             {                 credentials: 'XXXXXXXXXXXXXXXXXXX',                 center: StartPoint,                 zoom: 18,                 mapTypeId: Microsoft.Maps.MapTypeId.aerial             });           // place two markers         marker1 = PlaceMarker(new Microsoft.Maps.Location(StartLat, StartLng + .0001));         marker2 = PlaceMarker(new Microsoft.Maps.Location(StartLat, StartLng - .0001));           DragEnd(null);     } Note: In the Bing documentation, mapTypeId: was missing from the list of options even though the sample code included it. Note: When creating the Bing map, use the developer Key for the credentials property. I immediately place two markers/pins on the map which is simpler that creating them on the fly with mouse clicks (as I first tried). The markers/pins are draggable and I capture the DragEnd event to calculate and display the distance in yards and draw a line when the user finishes dragging. Here is the code to place a marker: Google: // ---- PlaceMarker ------------------------------------   function PlaceMarker(location) {     var marker = new google.maps.Marker(         {             position: location,             map: gTheMap,             draggable: true         });     marker.addListener('dragend', DragEnd);     return marker; } Bing: // ---- PlaceMarker ------------------------------------   function PlaceMarker(location) {     var marker = new Microsoft.Maps.Pushpin(location,     {         draggable : true     });     Microsoft.Maps.Events.addHandler(marker, 'dragend', DragEnd);     gTheMap.entities.push(marker);     return marker; } Here is the code than runs when the user stops dragging a marker: Google: // ---- DragEnd -------------------------------------------   var gLine = null;   function DragEnd(Event) {     var meters = google.maps.geometry.spherical.computeDistanceBetween(marker1.position, marker2.position);     var yards = meters * 1.0936133;     $("#message").text(yards.toFixed(1) + ' yards');    // draw a line connecting the points     var Endpoints = [marker1.position, marker2.position];       if (gLine == null)     {         gLine = new google.maps.Polyline({             path: Endpoints,             strokeColor: "#FFFF00",             strokeOpacity: 1.0,             strokeWeight: 2,             map: gTheMap         });     }     else        gLine.setPath(Endpoints); } Bing: // ---- DragEnd -------------------------------------------   var gLine = null;   function DragEnd(Args) {    var Distance =  CalculateDistance(marker1._location, marker2._location);      $("#message").text(Distance.toFixed(1) + ' yards');       // draw a line connecting the points    var Endpoints = [marker1._location, marker2._location];           if (gLine == null)    {        gLine = new Microsoft.Maps.Polyline(Endpoints,            {                strokeColor: new Microsoft.Maps.Color(0xFF, 0xFF, 0xFF, 0),  // aRGB                strokeThickness : 2            });          gTheMap.entities.push(gLine);    }    else        gLine.setLocations(Endpoints);  }  Note: I couldn't find a function to calculate the distance between points in the Bing API, so I wrote my own (CalculateDistance). If you want to see the source for it, you can pick it off the web page. Note: I was able to verify the accuracy of the measurements by using the golf hole next to the field. I put a pin/marker on the center of the green, and then by zooming in, I was able to see the 150 markers on the fairway and put the other pin/marker on one of them. Final Notes: All in all, the APIs are very similar. Both made it easy to accomplish a lot with a minimum amount of code. In one aerial view, there are leaves on the tree, in the other, the trees are bare. I don't know which service has the newer data. Here are links to working pages: Bing Map Demo Google Map Demo I hope someone finds this useful. Steve Wellens   CodeProject

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  • How to Hashtag (Without Being #Annoying)

    - by Mike Stiles
    The right tool in the wrong hands can be a dangerous thing. Giving a chimpanzee a chain saw would not be a pretty picture. And putting Twitter hashtags in the hands of social marketers who were never really sure how to use them can be equally unattractive. Boiled down, hashtags are for search and organization of tweets. A notch up from that, they can also be used as part of a marketing strategy. In terms of search, if you’re in the organic apple business, you want anyone who searches “organic” on Twitter to see your posts about your apples. It’s keyword tactics not unlike web site keyword search tactics. So get a clear idea of what keywords are relevant for your tweet. It’s reasonable to include #organic in your tweet. Is it fatal if you don’t hashtag the word? It depends on the person searching. If they search “organic,” your tweet’s going to come up even if you didn’t put the hashtag in front of it. If the searcher enters “#organic,” your tweet needs the hashtag. Err on the side of caution and hashtag it so it comes up no matter how the searcher enters it. You’ll also want to hashtag it for the second big reason people hashtag, organization. You can follow a hashtag. So can the rest of the Twitterverse. If you’re that into organic munchies, you can set up a stream populated only with tweets hashtagged #organic. If you’ve established a hashtag for your brand, like #nobugsprayapples, you (and everyone else) can watch what people are tweeting about your company. So what kind of hashtags should you include? They should be directly related to the core message of your tweet. Ancillary or very loosely-related hashtags = annoying. Hashtagging your brand makes sense. Hashtagging your core area of interest makes sense. Creating a specific event or campaign hashtag you want others to include and spread makes sense (the burden is on you to promote it and get it going). Hashtagging nearly every word in the tweet is highly annoying. Far and away, the majority of hashtagged words in such tweets have no relevance, are not terms that would be searched, and are not terms needed for categorization. It looks desperate and spammy. Two is fine. One is better. And it is possible to tweet with --gasp-- no hashtags! Make your hashtags as short as you can. In fact, if your brand’s name really is #nobugsprayapples, you’re burning up valuable, limited characters and risking the inability of others to retweet with added comments. Also try to narrow your topic hashtag down. You’ll find a lot of relevant users with #organic, but a lot of totally uninterested users with #food. Just as you can join online forums and gain credibility and a reputation by contributing regularly to that forum, you can follow hashtagged topics and gain the same kind of credibility in your area of expertise. Don’t just parachute in for the occasional marketing message. And if you’re constantly retweeting one particular person, stop it. It’s kissing up and it’s obvious. Which brings us to the king of hashtag annoyances, “hashjacking.” This is when you see what terms are hot and include them in your marketing tweet as a hashtag, even though it’s unrelated to your content. Justify it all you want, but #justinbieber has nothing to do with your organic apples. Equally annoying, piggybacking on a popular event’s hashtag to tweet something not connected to the event. You’re only fostering ill will and mistrust toward your account from the people you’ve tricked into seeing your tweet. Lastly, don’t @ mention people just to make sure they see your tweet. If the tweet’s not for them or about them, it’s spammy. What I haven’t covered is use of the hashtag for comedy’s sake. You’ll see this a lot and is a matter of personal taste. No one will search these hashtagged terms or need to categorize then, they’re just there for self-expression and laughs. Twitter is, after all, supposed to be fun.  What are some of your biggest Twitter pet peeves? #blogsovernow

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  • IsNumeric() Broken? Only up to a point.

    - by Phil Factor
    In SQL Server, probably the best-known 'broken' function is poor ISNUMERIC() . The documentation says 'ISNUMERIC returns 1 when the input expression evaluates to a valid numeric data type; otherwise it returns 0. ISNUMERIC returns 1 for some characters that are not numbers, such as plus (+), minus (-), and valid currency symbols such as the dollar sign ($).'Although it will take numeric data types (No, I don't understand why either), its main use is supposed to be to test strings to make sure that you can convert them to whatever numeric datatype you are using (int, numeric, bigint, money, smallint, smallmoney, tinyint, float, decimal, or real). It wouldn't actually be of much use anyway, since each datatype has different rules. You actually need a RegEx to do a reasonably safe check. The other snag is that the IsNumeric() function  is a bit broken. SELECT ISNUMERIC(',')This cheerfully returns 1, since it believes that a comma is a currency symbol (not a thousands-separator) and you meant to say 0, in this strange currency.  However, SELECT ISNUMERIC(N'£')isn't recognized as currency.  '+' and  '-' is seen to be numeric, which is stretching it a bit. You'll see that what it allows isn't really broken except that it doesn't recognize Unicode currency symbols: It just tells you that one numeric type is likely to accept the string if you do an explicit conversion to it using the string. Both these work fine, so poor IsNumeric has to follow suit. SELECT  CAST('0E0' AS FLOAT)SELECT  CAST (',' AS MONEY) but it is harder to predict which data type will accept a '+' sign. SELECT  CAST ('+' AS money) --0.00SELECT  CAST ('+' AS INT)   --0SELECT  CAST ('+' AS numeric)/* Msg 8115, Level 16, State 6, Line 4 Arithmetic overflow error converting varchar to data type numeric.*/SELECT  CAST ('+' AS FLOAT)/*Msg 8114, Level 16, State 5, Line 5Error converting data type varchar to float.*/> So we can begin to say that the maybe IsNumeric isn't really broken, but is answering a silly question 'Is there some numeric datatype to which i can convert this string? Almost, but not quite. The bug is that it doesn't understand Unicode currency characters such as the euro or franc which are actually valid when used in the CAST function. (perhaps they're delaying fixing the euro bug just in case it isn't necessary).SELECT ISNUMERIC (N'?23.67') --0SELECT  CAST (N'?23.67' AS money) --23.67SELECT ISNUMERIC (N'£100.20') --1SELECT  CAST (N'£100.20' AS money) --100.20 Also the CAST function itself is quirky in that it cannot convert perfectly reasonable string-representations of integers into integersSELECT ISNUMERIC('200,000')       --1SELECT  CAST ('200,000' AS INT)   --0/*Msg 245, Level 16, State 1, Line 2Conversion failed when converting the varchar value '200,000' to data type int.*/  A more sensible question is 'Is this an integer or decimal number'. This cuts out a lot of the apparent quirkiness. We do this by the '+E0' trick. If we want to include floats in the check, we'll need to make it a bit more complicated. Here is a small test-rig. SELECT  PossibleNumber,         ISNUMERIC(CAST(PossibleNumber AS NVARCHAR(20)) + 'E+00') AS Hack,        ISNUMERIC (PossibleNumber + CASE WHEN PossibleNumber LIKE '%E%'                                          THEN '' ELSE 'E+00' END) AS Hackier,        ISNUMERIC(PossibleNumber) AS RawIsNumericFROM    (SELECT CAST(',' AS NVARCHAR(10)) AS PossibleNumber          UNION SELECT '£' UNION SELECT '.'         UNION SELECT '56' UNION SELECT '456.67890'         UNION SELECT '0E0' UNION SELECT '-'         UNION SELECT '-' UNION SELECT '.'         UNION  SELECT N'?' UNION SELECT N'¢'        UNION  SELECT N'?' UNION SELECT N'?34.56'         UNION SELECT '-345' UNION SELECT '3.332228E+09') AS examples Which gives the result ... PossibleNumber Hack Hackier RawIsNumeric-------------- ----------- ----------- ------------? 0 0 0- 0 0 1, 0 0 1. 0 0 1¢ 0 0 1£ 0 0 1? 0 0 0?34.56 0 0 00E0 0 1 13.332228E+09 0 1 1-345 1 1 1456.67890 1 1 156 1 1 1 I suspect that this is as far as you'll get before you abandon IsNumeric in favour of a regex. You can only get part of the way with the LIKE wildcards, because you cannot specify quantifiers. You'll need full-blown Regex strings like these ..[-+]?\b[0-9]+(\.[0-9]+)?\b #INT or REAL[-+]?\b[0-9]{1,3}\b #TINYINT[-+]?\b[0-9]{1,5}\b #SMALLINT.. but you'll get even these to fail to catch numbers out of range.So is IsNumeric() an out and out rogue function? Not really, I'd say, but then it would need a damned good lawyer.

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  • Part 4 of 4 : Tips/Tricks for Silverlight Developers.

    - by mbcrump
    Part 1 | Part 2 | Part 3 | Part 4 I wanted to create a series of blog post that gets right to the point and is aimed specifically at Silverlight Developers. The most important things I want this series to answer is : What is it?  Why do I care? How do I do it? I hope that you enjoy this series. Let’s get started: Tip/Trick #16) What is it? Find out version information about Silverlight and which WebKit it is using by going to http://issilverlightinstalled.com/scriptverify/. Why do I care? I’ve had those users that its just easier to give them a site and say copy/paste the line that says User Agent in order to troubleshoot a Silverlight problem. I’ve also been debugging my own Silverlight applications and needed an easy way to determine if the plugin is disabled or not. How do I do it: Simply navigate to http://issilverlightinstalled.com/scriptverify/ and hit the Verify button. An example screenshot is located below: Results from Chrome 7 Results from Internet Explorer 8 (With Silverlight Disabled) Tip/Trick #17) What is it? Use Lambdas whenever you can. Why do I care?  It is my personal opinion that code is easier to read using Lambdas after you get past the syntax. How do I do it: For example: You may write code like the following: void MainPage_Loaded(object sender, RoutedEventArgs e) { //Check and see if we have a newer .XAP file on the server Application.Current.CheckAndDownloadUpdateAsync(); Application.Current.CheckAndDownloadUpdateCompleted += new CheckAndDownloadUpdateCompletedEventHandler(Current_CheckAndDownloadUpdateCompleted); } void Current_CheckAndDownloadUpdateCompleted(object sender, CheckAndDownloadUpdateCompletedEventArgs e) { if (e.UpdateAvailable) { MessageBox.Show( "An update has been installed. To see the updates please exit and restart the application"); } } To me this style forces me to look for the other Method to see what the code is actually doing. The style located below is much easier to read in my opinion and does the exact same thing. void MainPage_Loaded(object sender, RoutedEventArgs e) { //Check and see if we have a newer .XAP file on the server Application.Current.CheckAndDownloadUpdateAsync(); Application.Current.CheckAndDownloadUpdateCompleted += (s, e) => { if (e.UpdateAvailable) { MessageBox.Show( "An update has been installed. To see the updates please exit and restart the application"); } }; } Tip/Trick #18) What is it? Prevent development Web Service references from breaking when Visual Studio auto generates a new port number. Why do I care?  We have all been there, we are developing a Silverlight Application and all of a sudden our development web services break. We check and find out that the local port number that Visual Studio assigned has changed and now we need up to update all of our service references. We need a way to stop this. How do I do it: This can actually be prevented with just a few mouse click. Right click on your web solution and goto properties. Click the tab that says, Web. You just need to click the radio button and specify a port number. Now you won’t be bothered with that anymore. Tip/Trick #19) What is it? You can disable the Close Button a ChildWindow. Why do I care?  I wouldn’t blog about it if I hadn’t seen it. Devs trying to override keystrokes to prevent users from closing a Child Window. How do I do it: A property exist on the ChildWindow called “HasCloseButton”, you simply change that to false and your close button is gone. You can delete the “Cancel” button and add some logic to the OK button if you want the user to respond before proceeding. Tip/Trick #20) What is it? Cleanup your XAML. Why do I care?  By removing unneeded namespaces, not naming all of your controls and getting rid of designer markup you can improve code quality and readability. How do I do it: (This is a 3 in one tip) Remove unused Designer markup: 1) Have you ever wondered what the following code snippet does? xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480" This code is telling the designer to do something special with this page in “Design mode” Specifically the width and the height of the page. When its running in the browser it will not use this information and it is actually ignored by the XAML parser. In other words, if you don’t need it then delete it. 2) If you are not using a namespace then remove it. In the code sample below, I am using Resharper which will tell me the ones that I’m not using by the grayed out line below. If you don’t have resharper you can look in your XAML and manually remove the unneeded namespaces. 3) Don’t name an control unless you actually need to refer to it in procedural code. If you name a control you will take a slight performance hit that is totally unnecessary if its not being called. <TextBlock Height="23" Text="TextBlock" />   That is the end of the series. I hope that you enjoyed it and please check out Part 1 | Part 2 | Part 3 if your hungry for more.  Subscribe to my feed CodeProject

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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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  • C#/.NET Little Wonders: The Concurrent Collections (1 of 3)

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In the next few weeks, we will discuss the concurrent collections and how they have changed the face of concurrent programming. This week’s post will begin with a general introduction and discuss the ConcurrentStack<T> and ConcurrentQueue<T>.  Then in the following post we’ll discuss the ConcurrentDictionary<T> and ConcurrentBag<T>.  Finally, we shall close on the third post with a discussion of the BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. A brief history of collections In the beginning was the .NET 1.0 Framework.  And out of this framework emerged the System.Collections namespace, and it was good.  It contained all the basic things a growing programming language needs like the ArrayList and Hashtable collections.  The main problem, of course, with these original collections is that they held items of type object which means you had to be disciplined enough to use them correctly or you could end up with runtime errors if you got an object of a type you weren't expecting. Then came .NET 2.0 and generics and our world changed forever!  With generics the C# language finally got an equivalent of the very powerful C++ templates.  As such, the System.Collections.Generic was born and we got type-safe versions of all are favorite collections.  The List<T> succeeded the ArrayList and the Dictionary<TKey,TValue> succeeded the Hashtable and so on.  The new versions of the library were not only safer because they checked types at compile-time, in many cases they were more performant as well.  So much so that it's Microsoft's recommendation that the System.Collections original collections only be used for backwards compatibility. So we as developers came to know and love the generic collections and took them into our hearts and embraced them.  The problem is, thread safety in both the original collections and the generic collections can be problematic, for very different reasons. Now, if you are only doing single-threaded development you may not care – after all, no locking is required.  Even if you do have multiple threads, if a collection is “load-once, read-many” you don’t need to do anything to protect that container from multi-threaded access, as illustrated below: 1: public static class OrderTypeTranslator 2: { 3: // because this dictionary is loaded once before it is ever accessed, we don't need to synchronize 4: // multi-threaded read access 5: private static readonly Dictionary<string, char> _translator = new Dictionary<string, char> 6: { 7: {"New", 'N'}, 8: {"Update", 'U'}, 9: {"Cancel", 'X'} 10: }; 11:  12: // the only public interface into the dictionary is for reading, so inherently thread-safe 13: public static char? Translate(string orderType) 14: { 15: char charValue; 16: if (_translator.TryGetValue(orderType, out charValue)) 17: { 18: return charValue; 19: } 20:  21: return null; 22: } 23: } Unfortunately, most of our computer science problems cannot get by with just single-threaded applications or with multi-threading in a load-once manner.  Looking at  today's trends, it's clear to see that computers are not so much getting faster because of faster processor speeds -- we've nearly reached the limits we can push through with today's technologies -- but more because we're adding more cores to the boxes.  With this new hardware paradigm, it is even more important to use multi-threaded applications to take full advantage of parallel processing to achieve higher application speeds. So let's look at how to use collections in a thread-safe manner. Using historical collections in a concurrent fashion The early .NET collections (System.Collections) had a Synchronized() static method that could be used to wrap the early collections to make them completely thread-safe.  This paradigm was dropped in the generic collections (System.Collections.Generic) because having a synchronized wrapper resulted in atomic locks for all operations, which could prove overkill in many multithreading situations.  Thus the paradigm shifted to having the user of the collection specify their own locking, usually with an external object: 1: public class OrderAggregator 2: { 3: private static readonly Dictionary<string, List<Order>> _orders = new Dictionary<string, List<Order>>(); 4: private static readonly _orderLock = new object(); 5:  6: public void Add(string accountNumber, Order newOrder) 7: { 8: List<Order> ordersForAccount; 9:  10: // a complex operation like this should all be protected 11: lock (_orderLock) 12: { 13: if (!_orders.TryGetValue(accountNumber, out ordersForAccount)) 14: { 15: _orders.Add(accountNumber, ordersForAccount = new List<Order>()); 16: } 17:  18: ordersForAccount.Add(newOrder); 19: } 20: } 21: } Notice how we’re performing several operations on the dictionary under one lock.  With the Synchronized() static methods of the early collections, you wouldn’t be able to specify this level of locking (a more macro-level).  So in the generic collections, it was decided that if a user needed synchronization, they could implement their own locking scheme instead so that they could provide synchronization as needed. The need for better concurrent access to collections Here’s the problem: it’s relatively easy to write a collection that locks itself down completely for access, but anything more complex than that can be difficult and error-prone to write, and much less to make it perform efficiently!  For example, what if you have a Dictionary that has frequent reads but in-frequent updates?  Do you want to lock down the entire Dictionary for every access?  This would be overkill and would prevent concurrent reads.  In such cases you could use something like a ReaderWriterLockSlim which allows for multiple readers in a lock, and then once a writer grabs the lock it blocks all further readers until the writer is done (in a nutshell).  This is all very complex stuff to consider. Fortunately, this is where the Concurrent Collections come in.  The Parallel Computing Platform team at Microsoft went through great pains to determine how to make a set of concurrent collections that would have the best performance characteristics for general case multi-threaded use. Now, as in all things involving threading, you should always make sure you evaluate all your container options based on the particular usage scenario and the degree of parallelism you wish to acheive. This article should not be taken to understand that these collections are always supperior to the generic collections. Each fills a particular need for a particular situation. Understanding what each container is optimized for is key to the success of your application whether it be single-threaded or multi-threaded. General points to consider with the concurrent collections The MSDN points out that the concurrent collections all support the ICollection interface. However, since the collections are already synchronized, the IsSynchronized property always returns false, and SyncRoot always returns null.  Thus you should not attempt to use these properties for synchronization purposes. Note that since the concurrent collections also may have different operations than the traditional data structures you may be used to.  Now you may ask why they did this, but it was done out of necessity to keep operations safe and atomic.  For example, in order to do a Pop() on a stack you have to know the stack is non-empty, but between the time you check the stack’s IsEmpty property and then do the Pop() another thread may have come in and made the stack empty!  This is why some of the traditional operations have been changed to make them safe for concurrent use. In addition, some properties and methods in the concurrent collections achieve concurrency by creating a snapshot of the collection, which means that some operations that were traditionally O(1) may now be O(n) in the concurrent models.  I’ll try to point these out as we talk about each collection so you can be aware of any potential performance impacts.  Finally, all the concurrent containers are safe for enumeration even while being modified, but some of the containers support this in different ways (snapshot vs. dirty iteration).  Once again I’ll highlight how thread-safe enumeration works for each collection. ConcurrentStack<T>: The thread-safe LIFO container The ConcurrentStack<T> is the thread-safe counterpart to the System.Collections.Generic.Stack<T>, which as you may remember is your standard last-in-first-out container.  If you think of algorithms that favor stack usage (for example, depth-first searches of graphs and trees) then you can see how using a thread-safe stack would be of benefit. The ConcurrentStack<T> achieves thread-safe access by using System.Threading.Interlocked operations.  This means that the multi-threaded access to the stack requires no traditional locking and is very, very fast! For the most part, the ConcurrentStack<T> behaves like it’s Stack<T> counterpart with a few differences: Pop() was removed in favor of TryPop() Returns true if an item existed and was popped and false if empty. PushRange() and TryPopRange() were added Allows you to push multiple items and pop multiple items atomically. Count takes a snapshot of the stack and then counts the items. This means it is a O(n) operation, if you just want to check for an empty stack, call IsEmpty instead which is O(1). ToArray() and GetEnumerator() both also take snapshots. This means that iteration over a stack will give you a static view at the time of the call and will not reflect updates. Pushing on a ConcurrentStack<T> works just like you’d expect except for the aforementioned PushRange() method that was added to allow you to push a range of items concurrently. 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: // but you can also push multiple items in one atomic operation (no interleaves) 7: stack.PushRange(new [] { "Second", "Third", "Fourth" }); For looking at the top item of the stack (without removing it) the Peek() method has been removed in favor of a TryPeek().  This is because in order to do a peek the stack must be non-empty, but between the time you check for empty and the time you execute the peek the stack contents may have changed.  Thus the TryPeek() was created to be an atomic check for empty, and then peek if not empty: 1: // to look at top item of stack without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (stack.TryPeek(out item)) 5: { 6: Console.WriteLine("Top item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Stack was empty."); 11: } Finally, to remove items from the stack, we have the TryPop() for single, and TryPopRange() for multiple items.  Just like the TryPeek(), these operations replace Pop() since we need to ensure atomically that the stack is non-empty before we pop from it: 1: // to remove items, use TryPop or TryPopRange to get multiple items atomically (no interleaves) 2: if (stack.TryPop(out item)) 3: { 4: Console.WriteLine("Popped " + item); 5: } 6:  7: // TryPopRange will only pop up to the number of spaces in the array, the actual number popped is returned. 8: var poppedItems = new string[2]; 9: int numPopped = stack.TryPopRange(poppedItems); 10:  11: foreach (var theItem in poppedItems.Take(numPopped)) 12: { 13: Console.WriteLine("Popped " + theItem); 14: } Finally, note that as stated before, GetEnumerator() and ToArray() gets a snapshot of the data at the time of the call.  That means if you are enumerating the stack you will get a snapshot of the stack at the time of the call.  This is illustrated below: 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: var results = stack.GetEnumerator(); 7:  8: // but you can also push multiple items in one atomic operation (no interleaves) 9: stack.PushRange(new [] { "Second", "Third", "Fourth" }); 10:  11: while(results.MoveNext()) 12: { 13: Console.WriteLine("Stack only has: " + results.Current); 14: } The only item that will be printed out in the above code is "First" because the snapshot was taken before the other items were added. This may sound like an issue, but it’s really for safety and is more correct.  You don’t want to enumerate a stack and have half a view of the stack before an update and half a view of the stack after an update, after all.  In addition, note that this is still thread-safe, whereas iterating through a non-concurrent collection while updating it in the old collections would cause an exception. ConcurrentQueue<T>: The thread-safe FIFO container The ConcurrentQueue<T> is the thread-safe counterpart of the System.Collections.Generic.Queue<T> class.  The concurrent queue uses an underlying list of small arrays and lock-free System.Threading.Interlocked operations on the head and tail arrays.  Once again, this allows us to do thread-safe operations without the need for heavy locks! The ConcurrentQueue<T> (like the ConcurrentStack<T>) has some departures from the non-concurrent counterpart.  Most notably: Dequeue() was removed in favor of TryDequeue(). Returns true if an item existed and was dequeued and false if empty. Count does not take a snapshot It subtracts the head and tail index to get the count.  This results overall in a O(1) complexity which is quite good.  It’s still recommended, however, that for empty checks you call IsEmpty instead of comparing Count to zero. ToArray() and GetEnumerator() both take snapshots. This means that iteration over a queue will give you a static view at the time of the call and will not reflect updates. The Enqueue() method on the ConcurrentQueue<T> works much the same as the generic Queue<T>: 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5: queue.Enqueue("Second"); 6: queue.Enqueue("Third"); For front item access, the TryPeek() method must be used to attempt to see the first item if the queue.  There is no Peek() method since, as you’ll remember, we can only peek on a non-empty queue, so we must have an atomic TryPeek() that checks for empty and then returns the first item if the queue is non-empty. 1: // to look at first item in queue without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (queue.TryPeek(out item)) 5: { 6: Console.WriteLine("First item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Queue was empty."); 11: } Then, to remove items you use TryDequeue().  Once again this is for the same reason we have TryPeek() and not Peek(): 1: // to remove items, use TryDequeue. If queue is empty returns false. 2: if (queue.TryDequeue(out item)) 3: { 4: Console.WriteLine("Dequeued first item " + item); 5: } Just like the concurrent stack, the ConcurrentQueue<T> takes a snapshot when you call ToArray() or GetEnumerator() which means that subsequent updates to the queue will not be seen when you iterate over the results.  Thus once again the code below will only show the first item, since the other items were added after the snapshot. 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5:  6: var iterator = queue.GetEnumerator(); 7:  8: queue.Enqueue("Second"); 9: queue.Enqueue("Third"); 10:  11: // only shows First 12: while (iterator.MoveNext()) 13: { 14: Console.WriteLine("Dequeued item " + iterator.Current); 15: } Using collections concurrently You’ll notice in the examples above I stuck to using single-threaded examples so as to make them deterministic and the results obvious.  Of course, if we used these collections in a truly multi-threaded way the results would be less deterministic, but would still be thread-safe and with no locking on your part required! For example, say you have an order processor that takes an IEnumerable<Order> and handles each other in a multi-threaded fashion, then groups the responses together in a concurrent collection for aggregation.  This can be done easily with the TPL’s Parallel.ForEach(): 1: public static IEnumerable<OrderResult> ProcessOrders(IEnumerable<Order> orderList) 2: { 3: var proxy = new OrderProxy(); 4: var results = new ConcurrentQueue<OrderResult>(); 5:  6: // notice that we can process all these in parallel and put the results 7: // into our concurrent collection without needing any external locking! 8: Parallel.ForEach(orderList, 9: order => 10: { 11: var result = proxy.PlaceOrder(order); 12:  13: results.Enqueue(result); 14: }); 15:  16: return results; 17: } Summary Obviously, if you do not need multi-threaded safety, you don’t need to use these collections, but when you do need multi-threaded collections these are just the ticket! The plethora of features (I always think of the movie The Three Amigos when I say plethora) built into these containers and the amazing way they acheive thread-safe access in an efficient manner is wonderful to behold. Stay tuned next week where we’ll continue our discussion with the ConcurrentBag<T> and the ConcurrentDictionary<TKey,TValue>. For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here.   Tweet Technorati Tags: C#,.NET,Concurrent Collections,Collections,Multi-Threading,Little Wonders,BlackRabbitCoder,James Michael Hare

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  • Custom fail2ban Filter

    - by Michael Robinson
    In my quest to block excessive failed phpMyAdmin login attempts with fail2ban, I've created a script that logs said failed attempts to a file: /var/log/phpmyadmin_auth.log Custom log The format of the /var/log/phpmyadmin_auth.log file is: phpMyadmin login failed with username: root; ip: 192.168.1.50; url: http://somedomain.com/phpmyadmin/index.php phpMyadmin login failed with username: ; ip: 192.168.1.50; url: http://192.168.1.48/phpmyadmin/index.php Custom filter [Definition] # Count all bans in the logfile failregex = phpMyadmin login failed with username: .*; ip: <HOST>; phpMyAdmin jail [phpmyadmin] enabled = true port = http,https filter = phpmyadmin action = sendmail-whois[name=HTTP] logpath = /var/log/phpmyadmin_auth.log maxretry = 6 The fail2ban log contains: 2012-10-04 10:52:22,756 fail2ban.server : INFO Stopping all jails 2012-10-04 10:52:23,091 fail2ban.jail : INFO Jail 'ssh-iptables' stopped 2012-10-04 10:52:23,866 fail2ban.jail : INFO Jail 'fail2ban' stopped 2012-10-04 10:52:23,994 fail2ban.jail : INFO Jail 'ssh' stopped 2012-10-04 10:52:23,994 fail2ban.server : INFO Exiting Fail2ban 2012-10-04 10:52:24,253 fail2ban.server : INFO Changed logging target to /var/log/fail2ban.log for Fail2ban v0.8.6 2012-10-04 10:52:24,253 fail2ban.jail : INFO Creating new jail 'ssh' 2012-10-04 10:52:24,253 fail2ban.jail : INFO Jail 'ssh' uses poller 2012-10-04 10:52:24,260 fail2ban.filter : INFO Added logfile = /var/log/auth.log 2012-10-04 10:52:24,260 fail2ban.filter : INFO Set maxRetry = 6 2012-10-04 10:52:24,261 fail2ban.filter : INFO Set findtime = 600 2012-10-04 10:52:24,261 fail2ban.actions: INFO Set banTime = 600 2012-10-04 10:52:24,279 fail2ban.jail : INFO Creating new jail 'ssh-iptables' 2012-10-04 10:52:24,279 fail2ban.jail : INFO Jail 'ssh-iptables' uses poller 2012-10-04 10:52:24,279 fail2ban.filter : INFO Added logfile = /var/log/auth.log 2012-10-04 10:52:24,280 fail2ban.filter : INFO Set maxRetry = 5 2012-10-04 10:52:24,280 fail2ban.filter : INFO Set findtime = 600 2012-10-04 10:52:24,280 fail2ban.actions: INFO Set banTime = 600 2012-10-04 10:52:24,287 fail2ban.jail : INFO Creating new jail 'fail2ban' 2012-10-04 10:52:24,287 fail2ban.jail : INFO Jail 'fail2ban' uses poller 2012-10-04 10:52:24,287 fail2ban.filter : INFO Added logfile = /var/log/fail2ban.log 2012-10-04 10:52:24,287 fail2ban.filter : INFO Set maxRetry = 3 2012-10-04 10:52:24,288 fail2ban.filter : INFO Set findtime = 604800 2012-10-04 10:52:24,288 fail2ban.actions: INFO Set banTime = 604800 2012-10-04 10:52:24,292 fail2ban.jail : INFO Jail 'ssh' started 2012-10-04 10:52:24,293 fail2ban.jail : INFO Jail 'ssh-iptables' started 2012-10-04 10:52:24,297 fail2ban.jail : INFO Jail 'fail2ban' started When I issue: sudo service fail2ban restart fail2ban emails me to say ssh has restarted, but I receive no such email about my phpmyadmin jail. Repeated failed logins to phpMyAdmin does not cause an email to be sent. Have I missed some critical setup? Is my filter's regular expression wrong? Update: added changes from default installation Starting with a clean fail2ban installation: cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local Change email address to my own, action to: action = %(action_mwl)s Append the following to jail.local [phpmyadmin] enabled = true port = http,https filter = phpmyadmin action = sendmail-whois[name=HTTP] logpath = /var/log/phpmyadmin_auth.log maxretry = 4 Add the following to /etc/fail2ban/filter.d/phpmyadmin.conf # phpmyadmin configuration file # # Author: Michael Robinson # [Definition] # Option: failregex # Notes.: regex to match the password failures messages in the logfile. The # host must be matched by a group named "host". The tag "<HOST>" can # be used for standard IP/hostname matching and is only an alias for # (?:::f{4,6}:)?(?P<host>\S+) # Values: TEXT # # Count all bans in the logfile failregex = phpMyadmin login failed with username: .*; ip: <HOST>; # Option: ignoreregex # Notes.: regex to ignore. If this regex matches, the line is ignored. # Values: TEXT # # Ignore our own bans, to keep our counts exact. # In your config, name your jail 'fail2ban', or change this line! ignoreregex = Restart fail2ban sudo service fail2ban restart PS: I like eggs

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  • Custom fail2ban Filter for phpMyadmin bruteforce attempts

    - by Michael Robinson
    In my quest to block excessive failed phpMyAdmin login attempts with fail2ban, I've created a script that logs said failed attempts to a file: /var/log/phpmyadmin_auth.log Custom log The format of the /var/log/phpmyadmin_auth.log file is: phpMyadmin login failed with username: root; ip: 192.168.1.50; url: http://somedomain.com/phpmyadmin/index.php phpMyadmin login failed with username: ; ip: 192.168.1.50; url: http://192.168.1.48/phpmyadmin/index.php Custom filter [Definition] # Count all bans in the logfile failregex = phpMyadmin login failed with username: .*; ip: <HOST>; phpMyAdmin jail [phpmyadmin] enabled = true port = http,https filter = phpmyadmin action = sendmail-whois[name=HTTP] logpath = /var/log/phpmyadmin_auth.log maxretry = 6 The fail2ban log contains: 2012-10-04 10:52:22,756 fail2ban.server : INFO Stopping all jails 2012-10-04 10:52:23,091 fail2ban.jail : INFO Jail 'ssh-iptables' stopped 2012-10-04 10:52:23,866 fail2ban.jail : INFO Jail 'fail2ban' stopped 2012-10-04 10:52:23,994 fail2ban.jail : INFO Jail 'ssh' stopped 2012-10-04 10:52:23,994 fail2ban.server : INFO Exiting Fail2ban 2012-10-04 10:52:24,253 fail2ban.server : INFO Changed logging target to /var/log/fail2ban.log for Fail2ban v0.8.6 2012-10-04 10:52:24,253 fail2ban.jail : INFO Creating new jail 'ssh' 2012-10-04 10:52:24,253 fail2ban.jail : INFO Jail 'ssh' uses poller 2012-10-04 10:52:24,260 fail2ban.filter : INFO Added logfile = /var/log/auth.log 2012-10-04 10:52:24,260 fail2ban.filter : INFO Set maxRetry = 6 2012-10-04 10:52:24,261 fail2ban.filter : INFO Set findtime = 600 2012-10-04 10:52:24,261 fail2ban.actions: INFO Set banTime = 600 2012-10-04 10:52:24,279 fail2ban.jail : INFO Creating new jail 'ssh-iptables' 2012-10-04 10:52:24,279 fail2ban.jail : INFO Jail 'ssh-iptables' uses poller 2012-10-04 10:52:24,279 fail2ban.filter : INFO Added logfile = /var/log/auth.log 2012-10-04 10:52:24,280 fail2ban.filter : INFO Set maxRetry = 5 2012-10-04 10:52:24,280 fail2ban.filter : INFO Set findtime = 600 2012-10-04 10:52:24,280 fail2ban.actions: INFO Set banTime = 600 2012-10-04 10:52:24,287 fail2ban.jail : INFO Creating new jail 'fail2ban' 2012-10-04 10:52:24,287 fail2ban.jail : INFO Jail 'fail2ban' uses poller 2012-10-04 10:52:24,287 fail2ban.filter : INFO Added logfile = /var/log/fail2ban.log 2012-10-04 10:52:24,287 fail2ban.filter : INFO Set maxRetry = 3 2012-10-04 10:52:24,288 fail2ban.filter : INFO Set findtime = 604800 2012-10-04 10:52:24,288 fail2ban.actions: INFO Set banTime = 604800 2012-10-04 10:52:24,292 fail2ban.jail : INFO Jail 'ssh' started 2012-10-04 10:52:24,293 fail2ban.jail : INFO Jail 'ssh-iptables' started 2012-10-04 10:52:24,297 fail2ban.jail : INFO Jail 'fail2ban' started When I issue: sudo service fail2ban restart fail2ban emails me to say ssh has restarted, but I receive no such email about my phpmyadmin jail. Repeated failed logins to phpMyAdmin does not cause an email to be sent. Have I missed some critical setup? Is my filter's regular expression wrong? Update: added changes from default installation Starting with a clean fail2ban installation: cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local Change email address to my own, action to: action = %(action_mwl)s Append the following to jail.local [phpmyadmin] enabled = true port = http,https filter = phpmyadmin action = sendmail-whois[name=HTTP] logpath = /var/log/phpmyadmin_auth.log maxretry = 4 Add the following to /etc/fail2ban/filter.d/phpmyadmin.conf # phpmyadmin configuration file # # Author: Michael Robinson # [Definition] # Option: failregex # Notes.: regex to match the password failures messages in the logfile. The # host must be matched by a group named "host". The tag "<HOST>" can # be used for standard IP/hostname matching and is only an alias for # (?:::f{4,6}:)?(?P<host>\S+) # Values: TEXT # # Count all bans in the logfile failregex = phpMyadmin login failed with username: .*; ip: <HOST>; # Option: ignoreregex # Notes.: regex to ignore. If this regex matches, the line is ignored. # Values: TEXT # # Ignore our own bans, to keep our counts exact. # In your config, name your jail 'fail2ban', or change this line! ignoreregex = Restart fail2ban sudo service fail2ban restart PS: I like eggs

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  • What's the difference between find and findstr commands in Windows?

    - by Prashant Bhate
    In Windows, what are the differences between find and findstr commands? Both seems to search text in files: find c:\>find /? Searches for a text string in a file or files. FIND [/V] [/C] [/N] [/I] [/OFF[LINE]] "string" [[drive:][path]filename[ ...]] /V Displays all lines NOT containing the specified string. /C Displays only the count of lines containing the string. /N Displays line numbers with the displayed lines. /I Ignores the case of characters when searching for the string. /OFF[LINE] Do not skip files with offline attribute set. "string" Specifies the text string to find. [drive:][path]filename Specifies a file or files to search. If a path is not specified, FIND searches the text typed at the prompt or piped from another command. findstr c:\>findstr /? Searches for strings in files. FINDSTR [/B] [/E] [/L] [/R] [/S] [/I] [/X] [/V] [/N] [/M] [/O] [/P] [/F:file] [/C:string] [/G:file] [/D:dir list] [/A:color attributes] [/OFF[LINE]] strings [[drive:][path]filename[ ...]] /B Matches pattern if at the beginning of a line. /E Matches pattern if at the end of a line. /L Uses search strings literally. /R Uses search strings as regular expressions. /S Searches for matching files in the current directory and all subdirectories. /I Specifies that the search is not to be case-sensitive. /X Prints lines that match exactly. /V Prints only lines that do not contain a match. /N Prints the line number before each line that matches. /M Prints only the filename if a file contains a match. /O Prints character offset before each matching line. /P Skip files with non-printable characters. /OFF[LINE] Do not skip files with offline attribute set. /A:attr Specifies color attribute with two hex digits. See "color /?" /F:file Reads file list from the specified file(/ stands for console). /C:string Uses specified string as a literal search string. /G:file Gets search strings from the specified file(/ stands for console). /D:dir Search a semicolon delimited list of directories strings Text to be searched for. [drive:][path]filename Specifies a file or files to search. Use spaces to separate multiple search strings unless the argument is prefixed with /C. For example, 'FINDSTR "hello there" x.y' searches for "hello" or "there" in file x.y. 'FINDSTR /C:"hello there" x.y' searches for "hello there" in file x.y. Regular expression quick reference: . Wildcard: any character * Repeat: zero or more occurances of previous character or class ^ Line position: beginning of line $ Line position: end of line [class] Character class: any one character in set [^class] Inverse class: any one character not in set [x-y] Range: any characters within the specified range \x Escape: literal use of metacharacter x \<xyz Word position: beginning of word xyz\> Word position: end of word For full information on FINDSTR regular expressions refer to the online Command Reference.

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  • Windows 8 Stuck on Start Screen File Search

    - by baturayd
    I have been searching someone else having the same issue but I couldn't find any. Here is my problem: I'm using Windows 8 Pro with Media Center. File search screen does not close itself after I make a file search within start screen. It stuck on that screen. I can't go back to desktop, therefore, task manager is inaccessible. Only way to get out of it is to sign out. It also looks like non-operational. It doesn't give me any result at all. It's just a blank screen with "Files" title. It used to work perfectly. Things I have done before coming here: Safe mode minimal boot to ensure no other 3rd party software interferes. sfc haven't found any inconsistencies. Search index has been rebuild. Normal boot with all 3rd party services and start-up items disabled. System restore to a date that I know this feature was functional. And by the way, I have installed all updates released so far. I strongly used file search via start menu back in Windows 7. This is an absolute game changer for me. I'm curious what causes this. I'll do a "system refresh" if I can't fix this. I'm working on it, I'll keep this thread updated should I find any fix. First update: I just discovered that file search screen gets stuck if it's invoked by typing query directly in start screen. It doesn't get stuck if it's invoked from win + x menu. I was able to "escape" from stuck screen with invoking it again by win + x menu. After rebuilding search index again, search suggestions started to appear again but still there is no file search functionality. Second update: "Results for" expression appears only for a second near to "Files" title when search is initialized. Third update: As a last resort, I finally tried to do a "System Refresh" which has also failed to refresh by giving an error after waiting almost 20 minutes at 99%. (Seriously?) After cold boot it began to undo changes. After changes were reverted, I boot the machine without doing anything further and bingo! Search began acting normal again. This is a totally weird solution. It obviously fixed certain system files during failed refresh, and kept those changes untouched because they were supposed to be that way at the first place. I'll keep this thread alive should anyone comes with a more logical explanation. Forth update: After a windows update, search functionality again stopped responding. It happened after a system update for the first time. Now I have a pretty good suspicion about system update, though I have no solid proof of its involvement with this problem.

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  • Expose UserControl property to XAML

    - by Jared
    WPF controls have certain properties (UserControl.Resources, UserControl.CommandBindings) that can have items added to them from the XAML of a user control declaration. Example: <UserControl ... > <UserControl.CommandBindings> ... </UserControl.CommandBindings> <UserControl.Resources> ... </UserControl.Resources> </UserControl> I have a new list property defined in my user control: public partial class ArchetypeControl : UserControl { ... public List<Object> UICommands { get; set; } I want to add items to this list like I can with resources and CommandBindings, but when I do this: <c:ArchetypeControl.UICommands> </c:ArchetypeControl.UICommands> I get the error "Error 4 The attachable property 'UICommands' was not found in type 'ArchetypeControl'. " Suggestions? - Given the comments, I've created a test control to show the entire code and reproduce the problem. I'm using visual studio 2010. <UserControl x:Class="ArchetypesUI.TestControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:c="clr-namespace:ArchetypesUI" mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300"> <c:TestControl.TestObject> </c:TestControl.TestObject> <Grid> </Grid> </UserControl> - namespace ArchetypesUI { /// <summary> /// Interaction logic for TestControl.xaml /// </summary> public partial class TestControl : UserControl { public Object TestObject { get; set; } public TestControl() { InitializeComponent(); } } } Now the error I get is "Error 2 The attached property 'TestControl.TestObject' is not defined on 'UserControl' or one of its base classes."

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  • MVVM load data during or after ViewModel construction?

    - by mkmurray
    My generic question is as the title states, is it best to load data during ViewModel construction or afterward through some Loaded event handling? I'm guessing the answer is after construction via some Loaded event handling, but I'm wondering how that is most cleanly coordinated between ViewModel and View? Here's more details about my situation and the particular problem I'm trying to solve: I am using the MVVM Light framework as well as Unity for DI. I have some nested Views, each bound to a corresponding ViewModel. The ViewModels are bound to each View's root control DataContext via the ViewModelLocator idea that Laurent Bugnion has put into MVVM Light. This allows for finding ViewModels via a static resource and for controlling the lifetime of ViewModels via a Dependency Injection framework, in this case Unity. It also allows for Expression Blend to see everything in regard to ViewModels and how to bind them. So anyway, I've got a parent View that has a ComboBox databound to an ObservableCollection in its ViewModel. The ComboBox's SelectedItem is also bound (two-way) to a property on the ViewModel. When the selection of the ComboBox changes, this is to trigger updates in other views and subviews. Currently I am accomplishing this via the Messaging system that is found in MVVM Light. This is all working great and as expected when you choose different items in the ComboBox. However, the ViewModel is getting its data during construction time via a series of initializing method calls. This seems to only be a problem if I want to control what the initial SelectedItem of the ComboBox is. Using MVVM Light's messaging system, I currently have it set up where the setter of the ViewModel's SelectedItem property is the one broadcasting the update and the other interested ViewModels register for the message in their constructors. It appears I am currently trying to set the SelectedItem via the ViewModel at construction time, which hasn't allowed sub-ViewModels to be constructed and register yet. What would be the cleanest way to coordinate the data load and initial setting of SelectedItem within the ViewModel? I really want to stick with putting as little in the View's code-behind as is reasonable. I think I just need a way for the ViewModel to know when stuff has Loaded and that it can then continue to load the data and finalize the setup phase. Thanks in advance for your responses.

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  • MSDTC - Communication with the underlying transaction manager has failed (Firewall open, MSDTC netwo

    - by SocialAddict
    I'm having problems with my ASP.NET web forms system. It worked on our test server but now we are putting it live one of the servers is within a DMZ and the SQL server is outside of that (on our network still though - although a different subnet) I have open up the firewall completely between these two boxes to see if that was the issue and it still gives the error message "Communication with the underlying transaction manager has failed" whenever we try and use the "TransactionScope". We can access the data for retrieval it's just transactions that break it. We have also used msdtc ping to test the connection and with the amendments on the firewall that pings successfully, but the same error occurs! How do i resolve this error? Any help would be great as we have a system to go live today. Panic :) Edit: I have created a more straightforward test page with a transaction as below and this works fine. Could a nested transaction cause this kind of error and if so why would this only cause an issue when using a live box in a dmz with a firewall? AuditRepository auditRepository = new AuditRepository(); try { using (TransactionScope scope = new TransactionScope()) { auditRepository.Add(DateTime.Now, 1, "TEST-TRANSACTIONS#1", 1); auditRepository.Save(); auditRepository.Add(DateTime.Now, 1, "TEST-TRANSACTIONS#2", 1); auditRepository.Save(); scope.Complete(); } } catch (Exception ex) { Response.Write("Test Error For Transaction: " + ex.Message + "<br />" + ex.StackTrace); } This is the ErrorStack we are getting when the problem occurs: at System.Transactions.TransactionInterop.GetOletxTransactionFromTransmitterPropigationToken(Byte[] propagationToken) at System.Transactions.TransactionStatePSPEOperation.PSPEPromote(InternalTransaction tx) at System.Transactions.TransactionStateDelegatedBase.EnterState(InternalTransaction tx) at System.Transactions.EnlistableStates.Promote(InternalTransaction tx) at System.Transactions.Transaction.Promote() at System.Transactions.TransactionInterop.ConvertToOletxTransaction(Transaction transaction) at System.Transactions.TransactionInterop.GetExportCookie(Transaction transaction, Byte[] whereabouts) at System.Data.SqlClient.SqlInternalConnection.GetTransactionCookie(Transaction transaction, Byte[] whereAbouts) at System.Data.SqlClient.SqlInternalConnection.EnlistNonNull(Transaction tx) at System.Data.SqlClient.SqlInternalConnection.Enlist(Transaction tx) at System.Data.SqlClient.SqlInternalConnectionTds.Activate(Transaction transaction) at System.Data.ProviderBase.DbConnectionInternal.ActivateConnection(Transaction transaction) at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) at System.Data.SqlClient.SqlConnection.Open() at System.Data.Linq.SqlClient.SqlConnectionManager.UseConnection(IConnectionUser user) at System.Data.Linq.SqlClient.SqlProvider.get_IsSqlCe() at System.Data.Linq.SqlClient.SqlProvider.InitializeProviderMode() at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.ChangeDirector.StandardChangeDirector.DynamicInsert(TrackedObject item) at System.Data.Linq.ChangeDirector.StandardChangeDirector.Insert(TrackedObject item) at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges() at RegBook.classes.DbBase.Save() at RegBook.usercontrols.BookingProcess.confirmBookingButton_Click(Object sender, EventArgs e)

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  • Dissertation about website and database security - in need of some pointers

    - by ClarkeyBoy
    Hi, I am on my dissertation in my final year at university at the moment. One of the areas I need to research is security - for both websites and for databases. I currently have sections on the following: Website Form security - such as data validation. This section is more about preventing errors made by legitimate users as much as possible rather than stopping hackers, for example comparing a field to a regular expression and giving them meaningful feedback on any errors which did occur so as to stop it happening again. Constraints. For example if a value must be true or false then use a checkbox. If it is likely to be one of several values then use a dropdown or a set of radio boxes, and so on. If the value is unpredictable then use regular expressions to limit what characters they are allowed to enter, and to restrict the length of the string, and sometimes to limit the format (such as for dates / times, post codes and so on). Sometimes you can limit permissions to the form. This is on the occasion that you know exactly who (whether it be peoples names or a group of people - such as administrators or employees) is going to need access to the form. Restricting permissions will stop members of the public from being able to access the form. Symbols or strings which could be used maliciously or cause the website to act incorrectly (such as the script tag) should be filtered out or html encoded. Captcha images can be used to prevent automated systems from filling in and submitting the form. There are some hacks for file uploads - such as using double extensions - which can allow hackers to upload malicious files. Databases (this is nowhere near done yet but the sections I have planned are listed below) SQL statements vs stored procedures Throwing an error when one of the variables contains particular characters or groups of characters (I cant remember what characters they are, but I have seen a message thrown back at me before where I have tried to enter html or something into a text area). SQL Injection - and ways around it, with some examples. Does anyone have any hints and tips on where I could go for some decent, reliable information either about these areas or about other areas of security that I could cover? Thanks in advance. Regards, Richard PS I am a complete newbie when it comes to security, so please be patient with me. If any of the information I have put down is wrong or could be sub-sectioned then please feel free to say so.

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  • Extracting pair member in lambda expressions and template typedef idiom

    - by Nazgob
    Hi, I have some complex types here so I decided to use nifty trick to have typedef on templated types. Then I have a class some_container that has a container as a member. Container is a vector of pairs composed of element and vector. I want to write std::find_if algorithm with lambda expression to find element that have certain value. To get the value I have to call first on pair and then get value from element. Below my std::find_if there is normal loop that does the trick. My lambda fails to compile. How to access value inside element which is inside pair? I use g++ 4.4+ and VS 2010 and I want to stick to boost lambda for now. #include <vector> #include <algorithm> #include <boost\lambda\lambda.hpp> #include <boost\lambda\bind.hpp> template<typename T> class element { public: T value; }; template<typename T> class element_vector_pair // idiom to have templated typedef { public: typedef std::pair<element<T>, std::vector<T> > type; }; template<typename T> class vector_containter // idiom to have templated typedef { public: typedef std::vector<typename element_vector_pair<T>::type > type; }; template<typename T> bool operator==(const typename element_vector_pair<T>::type & lhs, const typename element_vector_pair<T>::type & rhs) { return lhs.first.value == rhs.first.value; } template<typename T> class some_container { public: element<T> get_element(const T& value) const { std::find_if(container.begin(), container.end(), bind(&typename vector_containter<T>::type::value_type::first::value, boost::lambda::_1) == value); /*for(size_t i = 0; i < container.size(); ++i) { if(container.at(i).first.value == value) { return container.at(i); } }*/ return element<T>(); //whatever } protected: typename vector_containter<T>::type container; }; int main() { some_container<int> s; s.get_element(5); return 0; }

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  • Silverlight Update/Trigger IValueConverter in Listbox DataTemplate in a DataGrid

    - by LJ
    Hi I am building an application to display a datagrid bound to an ObservableCollection of Records, where each record has a Course Object and an ObservableCollection of Results Objects. The course is changed using an autocomplete box. The results collection is displayed in a Listbox with an IValueConverter implementation to change the colour of the ellipse template based on criteria of the course currently selected. It works great on loading, but subsequent updates to the course selection via the autocomplete does not trigger a recalculation/refresh of the value converter. Is there a way to trigger the refresh in XAML. I added UpdateSource=Property changed to the binding of the list box - but this caused a stack overflow (haha). Here is the code: <data:DataGrid x:Name="MyDatGrid"> <data:DataGrid.Columns> <data:DataGridTemplateColumn Header="Results"> <data:DataGridTemplateColumn.CellTemplate> <DataTemplate> <ListBox ItemsSource="{Binding ListOfResults}"> <ListBox.ItemsPanel> <ItemsPanelTemplate> <StackPanel Orientation="Horizontal"/> </ItemsPanelTemplate> </ListBox.ItemsPanel> <ListBox.ItemTemplate> <DataTemplate> <Ellipse Width="20" Height="20" Fill="{Binding Converter={StaticResource resultToBrushConverter} }" Stroke="Black" StrokeThickness="1" /> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </DataTemplate> </data:DataGridTemplateColumn.CellTemplate> </data:DataGridTemplateColumn> <data:DataGridTemplateColumn Header="Course" > <data:DataGridTemplateColumn.CellTemplate> <DataTemplate> <Border> <input:AutoCompleteBox ItemsSource="{Binding Courses, Source={StaticResource coursesSource}}"/> </Border> </DataTemplate> </data:DataGridTemplateColumn.CellTemplate> I managed to subscribe to the LostFocus Event on the autocomplete box and reset a filter that I already have on the datagrid. But isn;t this very inefficient ? Refreshing the view on the datagrid does not have any effect in that method. Any steps in the right direction are greatly appreciated. Trying to prevent myself going anymore grey :) Had thoughts of getting the binding expression of the list in the grid and updating it, but no clue ? Thanks guys

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