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  • Image Steganography

    - by Sridhar
    Hi, I'm working on Steganography application. I need to hide a message inside an image file and secure it with a password, with not much difference in the file size. I am using Least Significant Bit algorithm and could do it successfully with BMP files but it does not work with JPEG, PNG or TIFF files. Does this algorithm work with these files at all? Is there a better way to achieve this? Thanks.

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  • Longest Common Subsequence

    - by tsudot
    Consider 2 sequences X[1..m] and Y[1..n]. The memoization algorithm would compute the LCS in time O(m*n). Is there any better algorithm to find out LCS wrt time? I guess memoization done diagonally can give us O(min(m,n)) time complexity.

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  • Sequential (comb) GUIDs for Oracle

    - by Eyvind
    We are in the process of switching from the C# Guid.NewGuid() random-ish guid generator to the sequential guid algorithm suggested in this post. While this seems to work well for MS SQL Server, I am unsure about the implications for Oracle databases, in which we store guids in a raw(16) field. Does anyone have any insight as to whether this algorithm would be good for creating sequential guids for Oracle as well as for MS SQL Server, or if a different variant should be used. Thanks!

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  • Big O and Little o

    - by hyperdude
    If algorithm A has complexity O(n) and algorithm B has complexity o(n^2), what, if anything, can we say about the relationship between A and B? Note: the complexity of A is expressed using big-Oh, and the complexity of B is expressed using little-Oh.

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  • Decision region plot for neural network in matlab

    - by Taban
    I have a neural network trained with backpropagation algorithm. I also create data set (input and target) random. Now I want to plot a decision region where each region is marked with a red star or with a blue circle according to whether it belongs to class 1 or -1. I searched a lot but just find plotpc function that is for perceptron algorithm. What should I try now? Any link or answer really helps. Thanks

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  • implementation of a queue using a circular array

    - by matin1234
    Hi I have found these algorithms in the internet but I can not understand that why in the enqueue method we compare size with N-1??? please help me thanks!! Algorithm size(): return (N-f+r)mod N Algorithm enqueue(e): if size()=N-1 then throw a FullQueueException Q[r]<---e r<----(r+1)mod N

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  • boost::regex_replace() replaces only first occurrence, why?

    - by Vincenzo
    My code: #include <string> #include <boost/algorithm/string/regex.hpp> std::cout << boost::algorithm::replace_regex_copy( "{x}{y}", // source string boost::regex("\\{.*?\\}"), // what to find std::string("{...}") // what to replace to ); This is what I see: {…}{y} Thus, only the first occurrence replaced. Why? How to solve it?

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  • Determining if two lines intersect

    - by Faken
    I have two lines that extend to infinity but both have a starting point. They are both described by a starting point and a vector in the direction of the line extending to infinity. I want to find out if the two lines intersect but i don't need to know where they intersect (its part of a collision detection algorithm). Everything i have looked at so far describes finding the intersection point of two lines or line segments. Anyone know a fast algorithm to solve this?

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  • Reflection problem - Type Safety Warning

    - by jax
    Class<? extends Algorithm> alg = AlgorithmAllFrom9AndLastFrom10Impl.class Constructor<Algorithm> c = alg.getConstructors()[0]; For "alg.getConstructors()[0];" I am getting a warning in eclipse Type safety: The expression of type Constructor needs unchecked conversion to conform to Constructor How do I fix this?

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  • How to calculate the cycles that change one permutation into another?

    - by fortran
    Hi, I'm looking for an algorithm that given two permutations of a sequence (e.g. [2, 3, 1, 4] and [4, 1, 3, 2]) calculates the cycles that are needed to convert the first into the second (for the example, [[0, 3], [1, 2]]). The link from mathworld says that Mathematica's ToCycle function does that, but sadly I don't have any Mathematica license at hand... I'd gladly receive any pointer to an implementation of the algorithm in any FOSS language or mathematics package. Thanks!

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  • How to compare two vectors, in C++

    - by Vincenzo
    This is my code: #include <algorithm> void f() { int[] a = {1, 2, 3, 4}; int[] b = {1, 2, 100, 101}; // I want to do something like this: // int* found = compare(a[0], a[3], b[0]); // in order to get a pointer to a[2] } Maybe I missed this algorithm in the manual… Please help :)

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  • Reverse web proxy with time constraints

    - by user2893458
    I have a web application which produces several unique URLs of the type http://service.company.com/service.html?type=aaaa&key=jfiZm6u6cW where the last part is a randomly generated key. Each such URL provides access to an instance of the service provided. I am looking for a way to restrict access to those URLs based on time constraints, as an example URL#1 should be available between 8:00AM and 10:00AM on May 30, URL#2 should be available between 10:30AM and 12:00PM on May 31, and so on. I already have a resource scheduling application based on Drupal and would like to find a way to include those URLs as scheduled resources. The web application is deployed on Apache Tomcat, so I don't have the knowledge or the resources to alter it, therefore I thought that I could put some sort of reverse proxy in front of the web app that could implement the time constraint feature. In my thoughts the reverse proxy would allow or disallow access to each URL based on the rules that my scheduling application would provide. There may be other ways to deliver such a solution, but I can't think of anything better, so the question is: is there a reverse web proxy architecture that could allow access to the destination URLs based on time and date rules? Any other ideas are more than welcome.

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  • CodePlex Daily Summary for Tuesday, May 25, 2010

    CodePlex Daily Summary for Tuesday, May 25, 2010New ProjectsBibleNames: BibleNames BibleNames BibleNames BibleNames BibleNamesBing Search for PHP Developers: This is the Bing SDK for PHP, a toolkit that allows you to easily use Bing's API to fetch search results and use in your own application. The Bin...Fading Clock: Fading Clock is a normal clock that has the ability to fade in out. It's developed in C# as a Windows App in .net 2.0.Fuzzy string matching algorithm in C# and LINQ: Fuzzy matching strings. Find out how similar two string is, and find the best fuzzy matching string from a string table. Given a string (strA) and...HexTile editor: Testing hexagonal tile editorhgcheck12: hgcheck12Metaverse Router: Metaverse Router makes it easier for MIIS, ILM, FIM Sync engine administrators to manage multiple provisioning modules, turn on/off provisioning wi...MyVocabulary: Use MyVocabulary to structure and test the words you want to learn in a foreign language. This is a .net 3.5 windows forms application developed in...phpxw: Phpxw 是一个简易的PHP框架。以我自己的姓名命名的。 Phpxw is a simple PHP framework. Take my name named.Plop: Social networking wrappers and projects.PST Data Structure View Tool: PST Data Structure View Tool (PSTViewTool) is a tool supporting the PST file format documentation effort. It allows the user to browse the internal...PST File Format SDK: PST File Format SDK (pstsdk) is a cross platform header only C++ library for reading PST files.QWine: QWine is Queue Machine ApplicationSharePoint Cross Site Collection Security Trimmed Navigation: This SP2010 project will show security trimmed navigation that works across site collections. The project is written for SP2010, but can be easily ...SharePoint List Field Manager: The SharePoint List Field Manager allows users to manage the Boolean properties of a list such as Read Only, Hidden, Show in New Form etc... It sup...Silverlight Toolbar for DataGrid working with RIA Services or local data: DataGridToolbar contains two controls for Silverlight DataGrid designed for RIA Services and local data. It can be used to filter or remove a data,...SilverShader - Silverlight Pixel Shader Demos: SilverShader is an extensible Silverlight application that is used to demonstrate the effect of different pixel shaders. The shaders can be applied...SNCFT Gadget: Ce gadget permet de consulter les horaires des trains et de chercher des informations sur le site de la société nationale des chemins de fer tunisi...Software Transaction Memory: Software Transaction Memory for .NETStreamInsight Samples: This project contains sample code for StreamInsight, Microsoft's platform for complex event processing. The purpose of the samples is to provide a ...StyleAnalizer: A CSS parserSudoku (Multiplayer in RnD): Sudoku project was to practice on C# by making a desktop application using some algorithm Before this, I had worked on http://shaktisaran.tech.o...Tiplican: A small website built for the purpose of learning .Net 4 and MVC 2TPager: Mercurial pager with color support on Windowsunirca: UNIRCA projectWcfTrace: The WcfTrace is a easy way to collect information about WCF-service call order, processing time and etc. It's developed in C#.New ReleasesASP.NET TimePicker Control: 12 24 Hour Bug Fix: 12 24 Hour Bug FixASP.NET TimePicker Control: ASP.NET TimePicker Control: This release fixes a focus bug that manifests itself when switching focus between two different timepicker controls on the same page, and make chan...ASP.NET TimePicker Control: ASP.NET TimePicker Control - colon CSS Fix: Fixes ":" seperator placement issues being too hi and too low in IE and FireFox, respectively.ASP.NET TimePicker Control: Release fixes 24 Hour Mode Bug: Release fixes 24 Hour Mode BugBFBC2 PRoCon: PRoCon 0.5.1.1: Visit http://phogue.net/?p=604 for release notes.BFBC2 PRoCon: PRoCon 0.5.1.2: Release notes can be found at http://phogue.net/?p=604BFBC2 PRoCon: PRoCon 0.5.1.4: Ha.. choosing the "stable" option at the moment is a bit of a joke =\ Release notes at http://phogue.net/?p=604BFBC2 PRoCon: PRoCon 0.5.1.5: BWHAHAHA stable.. ha. Actually this ones looking pretty good now. http://phogue.net/?p=604Bojinx: Bojinx Core V4.5.14: Issues fixed in this release: Fixed an issue that caused referencePropertyName when used through a property configuration in the context to not wo...Bojinx: Bojinx Debugger V0.9B: Output trace and filtering that works with the Bojinx logger.CassiniDev - Cassini 3.5/4.0 Developers Edition: CassiniDev 3.5.1.5 and 4.0.1.5 beta3: Fixed fairly serious bug #13290 http://cassinidev.codeplex.com/WorkItem/View.aspx?WorkItemId=13290Content Rendering: Content Rendering API 1.0.0 Revision 46406: Initial releaseDeploy Workflow Manager: Deploy Workflow Manager Web Part v2: Recommend you test in your development environment first BEFORE using in production.dotSpatial: System.Spatial.Projections Zip May 24, 2010: Adds a new spherical projection.eComic: eComic 2010.0.0.2: Quick release to fix a couple of bugs found in the previous version. Version 2010.0.0.2 Fixed crash error when accessing the "Go To Page" dialog ...Exchange 2010 RBAC Editor (RBAC GUI) - updated on 5/24/2010: RBAC Editor 0.9.4.1: Some bugs fixed; support for unscopoedtoplevel (adding script is not working yet) Please use email address in About menu of the tool for any feedb...Facebook Graph Toolkit: Preview 1 Binaries: The first preview release of the toolkit. Not recommended for use in production, but enought to get started developing your app.Fading Clock: Clock.zip: Clock.zip is a zip file that contains the application Clock.exe.hgcheck12: Rel8082: Rel8082hgcheck12: scsc: scasMetaverse Router: Metaverse Router v1.0: Initial stable release (v.1.0.0.0) of Metaverse Router Working with: FIM 2010 Synchronization Engine ILM 2007 MIIS 2003MSTestGlider: MSTestGlider 1.5: What MSTestGlider 1.5.zip unzips to: http://i49.tinypic.com/2lcv4eg.png If you compile MSTestGlider from its source you will need to change the ou...MyVocabulary: Version 1.0: First releaseNLog - Advanced .NET Logging: Nightly Build 2010.05.24.001: Changes since the last build:2010-05-23 20:45:37 Jarek Kowalski fixed whitespace in NLog.wxs 2010-05-23 12:01:48 Jarek Kowalski BufferingTargetWra...NoteExpress User Tools (NEUT) - Do it by ourselves!: NoteExpress User Tools 2.0.0: 测试版本:NoteExpress 2.5.0.1154 +调整了Tab页的排列方式 注:2.0未做大的改动,仅仅是运行环境由原来的.net 3.5升级到4.0。openrs: Beta Release (Revision 1): This is the beta release of the openrs framework. Please make sure you submit issues in the issue tracker tab. As this is beta, extreme, flawless ...openrs: Revision 2: Revision 2 of the framework. Basic worker example as well as minor improvements on the auth packet.phpxw: Phpxw: Phpxw 1.0 phpxw 是一个简易的PHP框架。以我自己的姓名命名的。 Phpxw is a simple PHP framework. Take my name named. 支持基本的业务逻辑流程,功能模块化,实现了简易的模板技术,同时也可以支持外接模板引擎。 Support...sELedit: sELedit v1.1a: Fixed: clean file before overwriting Fixed: list57 will only created when eLC.Lists.length > 57sGSHOPedit: sGSHOPedit v1.0a: Fixed: bug with wrong item array re-size when adding items after deleting items Added: link to project page pwdatabase.com version is now selec...SharePoint Cross Site Collection Security Trimmed Navigation: Release 1.0.0.0: If you want just the .wsp, and start using this, you can grab it here. Just stsadm add/deploy to your website, and activate the feature as describ...Silverlight 4.0 Popup Menu: Context Menu for Silverlight 4.0 v1.24 Beta: - Updated the demo and added clipboard cut/copy and paste functionality. - Added delay on hover events for both parent and child menus. - Parent me...Silverlight Toolbar for DataGrid working with RIA Services or local data: DataGridToolBar Beta: For Silverlight 4.0sMAPtool: sMAPtool v0.7d (without Maps): Added: link to project pagesMODfix: sMODfix v1.0a: Added: Support for ECM v52 modelssNPCedit: sNPCedit v0.9a: browse source commits for all changes...SocialScapes: SocialScapes TwitterWidget 1.0.0: The SocialScapes TwitterWidget is a DotNetNuke Widget for displaying Twitter searches. This widget will be used to replace the twitter functionali...SQL Server 2005 and 2008 - Backup, Integrity Check and Index Optimization: 23 May 2010: This is the latest version of my solution for Backup, Integrity Check and Index Optimization in SQL Server 2005, SQL Server 2008 and SQL Server 200...sqwarea: Sqwarea 0.0.280.0 (alpha): This release brings a lot of improvements. We strongly recommend you to upgrade to this version.sTASKedit: sTASKedit v0.7c: Minor Changes in GUI & BehaviourSudoku (Multiplayer in RnD): Sudoku (Multiplayer in RnD) 1.0.0.0 source: Sudoku project was to practice on C# by making a desktop application using some algorithm Idea: The basic idea of algorithm is from http://www.ac...Sudoku (Multiplayer in RnD): Sudoku (Multiplayer in RnD) 1.0.0.1 source: Worked on user-interface, would improve it Sudoku project was to practice on C# by making a desktop application using some algorithm Idea: The b...TFS WorkItem Watcher: TFS WorkItem Watcher Version 1.0: This version contains the following new features: Added support to autodetect whether to start as a service or to start in console mode. The "-c" ...TfsPolicyPack: TfsPolicyPack 0.1: This is the first release of the TfsPolicyPack. This release includes the following policies: CustomRegexPathPolicythinktecture Starter STS (Community Edition): StarterSTS v1.1 CTP: Added ActAs / identity delegation support.TPager: TPager-20100524: TPager 2010-05-24 releaseTrance Layer: TranceLayer Transformer: Transformer is a Beta version 2, morphing from "Digger" to "Transformer" release cycle. It is intended to be used as a demonstration of muscles wh...TweetSharp: TweetSharp v1.0.0.0: Changes in v1.0.0Added 100% public code comments Bug fixes based on feedback from the Release Candidate Changes to handle Twitter schema additi...VCC: Latest build, v2.1.30524.0: Automatic drop of latest buildWCF Client Generator: Version 0.9.2.33468: Version 0.9.2.33468 Fixed: Nested enum types names are not handled correctly. Can't close Visual Studio if generated files are open when the code...Word 2007 Redaction Tool: Version 1.2: A minor update to the Word 2007 Redaction Tool. This version can be installed directly over any existing version. Updates to Version 1.2Fixed bugs:...xPollinate - Windows Live Writer Cross Post Plugin: 1.0.0.5 for WLW 14.0.8117.416: This version works with WLW 14.0.8117.416. This release includes a fix to enable publishing posts that have been opened directly from a blog, but ...Yet another developer blog - Examples: jQuery Autocomplete in ASP.NET MVC: This sample application shows how to use jQuery Autocomplete plugin in ASP.NET MVC. This application is accompanied by the following entry on Yet a...Most Popular ProjectsRawrWBFS ManagerAJAX Control ToolkitMicrosoft SQL Server Product Samples: DatabaseSilverlight ToolkitWindows Presentation Foundation (WPF)patterns & practices – Enterprise LibraryMicrosoft SQL Server Community & SamplesPHPExcelASP.NETMost Active Projectspatterns & practices – Enterprise LibraryRawrpatterns & practices: Windows Azure Security GuidanceSqlServerExtensionsGMap.NET - Great Maps for Windows Forms & PresentationMono.AddinsCaliburn: An Application Framework for WPF and SilverlightBlogEngine.NETIonics Isapi Rewrite FilterSQL Server PowerShell Extensions

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  • Hibernate session problem for transactions.

    - by Jani
    Hi all, I am new to hibernate and trying integrate hibernate with an existing spring based application. I configured session factory and transaction manager, transaction proxy template. I am also using Quartz scheduler in this application. When I run the application, I am getting the following exception. ERROR au.com.michaelpage.ctsgui.utils.OrganisationMergeProfileThread - Error while updating opportunity: Could not open Hibernate Session for transaction; nested exception is java.lang.IllegalStateException: Already value [org.springframework.jdbc.datasource.ConnectionHolder@9f6885] for key [weblogic.jdbc.common.internal.RmiDataSource@32b034] bound to thread [DefaultQuartzScheduler_Worker-0] My hibernate session configuration: <bean id="sessionFactoryAU" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource"> <ref bean="profileAU" /> </property> <property name="mappingResources"> <list> <value> /au/com/michaelpage/ctsgui/hibernate/dao/mappings/Opportunity.hbm.xml </value> <value> /au/com/michaelpage/ctsgui/hibernate/dao/mappings/Position.hbm.xml </value> <value> /au/com/michaelpage/ctsgui/hibernate/dao/mappings/EventRole.hbm.xml </value> </list> </property> <property name="hibernateProperties"> <props> <!-- Database Settings --> <prop key="hibernate.dialect"> org.hibernate.dialect.SybaseDialect </prop> <prop key="hibernate.query.factory_class"> org.hibernate.hql.ast.ASTQueryTranslatorFactory </prop> <!-- Cache settings --> <prop key="hibernate.cache.provider_class"> org.hibernate.cache.EhCacheProvider </prop> </props> </property> </bean> <!-- Transaction manager for a Hibernate SessionFactory --> <bean id="txManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory"> <ref bean="sessionFactoryAU" /> </property> </bean> <!-- Transaction template for Managers --> <bean id="txProxyTemplateHibernateProfileAU" abstract="true" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean"> <property name="transactionManager"> <ref bean="txManager" /> </property> <property name="transactionAttributes"> <props> <prop key="create*">PROPAGATION_REQUIRED</prop> <prop key="save*">PROPAGATION_REQUIRED</prop> <prop key="update*">PROPAGATION_REQUIRED</prop> <prop key="delete*">PROPAGATION_REQUIRED</prop> <prop key="remove*">PROPAGATION_REQUIRED</prop> <prop key="get*">PROPAGATION_SUPPORTS</prop> </props> </property> </bean> <bean id="organisationMergeProfileMgrAU" parent="txProxyTemplateHibernateProfileAU"> <property name="target"> <bean class="au.com.michaelpage.ctsgui.mgr.profile.OrganisationMergeProfileMgrImpl"> <property name="commonProfileDao"> <ref bean="commonProfileDaoAU" /> </property> <property name="organisationMergeProfileDao"> <ref bean="organisationMergeDaoAU" /> </property> <property name="hibernateOrganisationDAO"> <ref bean="hibernateOrganisationDAOAU" /> </property> <property name="hibernateOpportunityDAO"> <ref bean="hibernateOpportunityDAOAU" /> </property> <property name="hibernatePositionDAO"> <ref bean="hibernatePositionDAOAU" /> </property> <property name="hibernateEventRoleDAO"> <ref bean="hibernateEventRoleDAOAU" /> </property> </bean> </property> </bean> My Quartz scheduler configuration: <bean id="organisationMergeJobDetail" class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean"> <property name="targetObject" ref="organisationMergeJob" /> <property name="targetMethod" value="execute" /> <property name="concurrent" value="false" /> </bean> <bean id="organisationMergeProfileRegularCheckerTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerBean"> <property name="jobDetail" ref="organisationMergeJobDetail" /> <property name="repeatInterval"> <util:constant static-field="au.com.michaelpage.ctsgui.common.Constants.CHECK_FREQUENCY" /> </property> </bean> Here is the bean definition for 'organisationMergeJob' <bean id="organisationMergeJob" class="au.com.michaelpage.ctsgui.utils.OrganisationMergeProfileThread"> <property name="organisationMergeMgr" ref="organisationMergeMgr"/> </bean> <bean id="organisationMergeMgr" class="au.com.michaelpage.ctsgui.mgr.OrganisationMergeMgrImpl"> <property name="organisationMergeDao" ref="organisationMergeDao"/> </bean> Any help to solve this? Thank you in advance. Hi skaffman, Here is the stack trace of the error: Could not open Hibernate Session for transaction; nested exception is java.lang.IllegalStateException: Already value [org.springframework.jdbc.datasource.ConnectionHolder@5f2fb8] for key [weblogic.jdbc.common.internal.RmiDataSource@326b7b] bound to thread [DefaultQuartzScheduler_Worker-3] Caused by: java.lang.IllegalStateException: Already value [org.springframework.jdbc.datasource.ConnectionHolder@5f2fb8] for key [weblogic.jdbc.common.internal.RmiDataSource@326b7b] bound to thread [DefaultQuartzScheduler_Worker-3] at org.springframework.transaction.support.TransactionSynchronizationManager.bindResource(TransactionSynchronizationManager.java:163) at org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:526) at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:350) at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:262) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:101) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) at $Proxy73.updateEventRole(Unknown Source) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) at $Proxy73.updateEventRole(Unknown Source) at au.com.michaelpage.ctsgui.utils.OrganisationMergeProfileThread.execute(OrganisationMergeProfileThread.java:100) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:283) at org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean$MethodInvokingJob.executeInternal(MethodInvokingJobDetailFactoryBean.java:272) at org.springframework.scheduling.quartz.QuartzJobBean.execute(QuartzJobBean.java:86) at org.quartz.core.JobRunShell.run(JobRunShell.java:203) at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520) Thank you. Here is the bean definition for 'organisationMergeMgr' <bean id="organisationMergeMgr" class="au.com.michaelpage.ctsgui.mgr.OrganisationMergeMgrImpl"> <property name="organisationMergeDao" ref="organisationMergeDao"/> </bean>

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  • C#: LINQ vs foreach - Round 1.

    - by James Michael Hare
    So I was reading Peter Kellner's blog entry on Resharper 5.0 and its LINQ refactoring and thought that was very cool.  But that raised a point I had always been curious about in my head -- which is a better choice: manual foreach loops or LINQ?    The answer is not really clear-cut.  There are two sides to any code cost arguments: performance and maintainability.  The first of these is obvious and quantifiable.  Given any two pieces of code that perform the same function, you can run them side-by-side and see which piece of code performs better.   Unfortunately, this is not always a good measure.  Well written assembly language outperforms well written C++ code, but you lose a lot in maintainability which creates a big techncial debt load that is hard to offset as the application ages.  In contrast, higher level constructs make the code more brief and easier to understand, hence reducing technical cost.   Now, obviously in this case we're not talking two separate languages, we're comparing doing something manually in the language versus using a higher-order set of IEnumerable extensions that are in the System.Linq library.   Well, before we discuss any further, let's look at some sample code and the numbers.  First, let's take a look at the for loop and the LINQ expression.  This is just a simple find comparison:       // find implemented via LINQ     public static bool FindViaLinq(IEnumerable<int> list, int target)     {         return list.Any(item => item == target);     }         // find implemented via standard iteration     public static bool FindViaIteration(IEnumerable<int> list, int target)     {         foreach (var i in list)         {             if (i == target)             {                 return true;             }         }           return false;     }   Okay, looking at this from a maintainability point of view, the Linq expression is definitely more concise (8 lines down to 1) and is very readable in intention.  You don't have to actually analyze the behavior of the loop to determine what it's doing.   So let's take a look at performance metrics from 100,000 iterations of these methods on a List<int> of varying sizes filled with random data.  For this test, we fill a target array with 100,000 random integers and then run the exact same pseudo-random targets through both searches.                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     Any         10       26          0.00046             30.00%     Iteration   10       20          0.00023             -     Any         100      116         0.00201             18.37%     Iteration   100      98          0.00118             -     Any         1000     1058        0.01853             16.78%     Iteration   1000     906         0.01155             -     Any         10,000   10,383      0.18189             17.41%     Iteration   10,000   8843        0.11362             -     Any         100,000  104,004     1.8297              18.27%     Iteration   100,000  87,941      1.13163             -   The LINQ expression is running about 17% slower for average size collections and worse for smaller collections.  Presumably, this is due to the overhead of the state machine used to track the iterators for the yield returns in the LINQ expressions, which seems about right in a tight loop such as this.   So what about other LINQ expressions?  After all, Any() is one of the more trivial ones.  I decided to try the TakeWhile() algorithm using a Count() to get the position stopped like the sample Pete was using in his blog that Resharper refactored for him into LINQ:       // Linq form     public static int GetTargetPosition1(IEnumerable<int> list, int target)     {         return list.TakeWhile(item => item != target).Count();     }       // traditionally iterative form     public static int GetTargetPosition2(IEnumerable<int> list, int target)     {         int count = 0;           foreach (var i in list)         {             if(i == target)             {                 break;             }               ++count;         }           return count;     }   Once again, the LINQ expression is much shorter, easier to read, and should be easier to maintain over time, reducing the cost of technical debt.  So I ran these through the same test data:                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile   10       41          0.00041             128%     Iteration   10       18          0.00018             -     TakeWhile   100      171         0.00171             88%     Iteration   100      91          0.00091             -     TakeWhile   1000     1604        0.01604             94%     Iteration   1000     825         0.00825             -     TakeWhile   10,000   15765       0.15765             92%     Iteration   10,000   8204        0.08204             -     TakeWhile   100,000  156950      1.5695              92%     Iteration   100,000  81635       0.81635             -     Wow!  I expected some overhead due to the state machines iterators produce, but 90% slower?  That seems a little heavy to me.  So then I thought, well, what if TakeWhile() is not the right tool for the job?  The problem is TakeWhile returns each item for processing using yield return, whereas our for-loop really doesn't care about the item beyond using it as a stop condition to evaluate. So what if that back and forth with the iterator state machine is the problem?  Well, we can quickly create an (albeit ugly) lambda that uses the Any() along with a count in a closure (if a LINQ guru knows a better way PLEASE let me know!), after all , this is more consistent with what we're trying to do, we're trying to find the first occurence of an item and halt once we find it, we just happen to be counting on the way.  This mostly matches Any().       // a new method that uses linq but evaluates the count in a closure.     public static int TakeWhileViaLinq2(IEnumerable<int> list, int target)     {         int count = 0;         list.Any(item =>             {                 if(item == target)                 {                     return true;                 }                   ++count;                 return false;             });         return count;     }     Now how does this one compare?                         List<T> On 100,000 Iterations     Method         Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile      10       41          0.00041             128%     Any w/Closure  10       23          0.00023             28%     Iteration      10       18          0.00018             -     TakeWhile      100      171         0.00171             88%     Any w/Closure  100      116         0.00116             27%     Iteration      100      91          0.00091             -     TakeWhile      1000     1604        0.01604             94%     Any w/Closure  1000     1101        0.01101             33%     Iteration      1000     825         0.00825             -     TakeWhile      10,000   15765       0.15765             92%     Any w/Closure  10,000   10802       0.10802             32%     Iteration      10,000   8204        0.08204             -     TakeWhile      100,000  156950      1.5695              92%     Any w/Closure  100,000  108378      1.08378             33%     Iteration      100,000  81635       0.81635             -     Much better!  It seems that the overhead of TakeAny() returning each item and updating the state in the state machine is drastically reduced by using Any() since Any() iterates forward until it finds the value we're looking for -- for the task we're attempting to do.   So the lesson there is, make sure when you use a LINQ expression you're choosing the best expression for the job, because if you're doing more work than you really need, you'll have a slower algorithm.  But this is true of any choice of algorithm or collection in general.     Even with the Any() with the count in the closure it is still about 30% slower, but let's consider that angle carefully.  For a list of 100,000 items, it was the difference between 1.01 ms and 0.82 ms roughly in a List<T>.  That's really not that bad at all in the grand scheme of things.  Even running at 90% slower with TakeWhile(), for the vast majority of my projects, an extra millisecond to save potential errors in the long term and improve maintainability is a small price to pay.  And if your typical list is 1000 items or less we're talking only microseconds worth of difference.   It's like they say: 90% of your performance bottlenecks are in 2% of your code, so over-optimizing almost never pays off.  So personally, I'll take the LINQ expression wherever I can because they will be easier to read and maintain (thus reducing technical debt) and I can rely on Microsoft's development to have coded and unit tested those algorithm fully for me instead of relying on a developer to code the loop logic correctly.   If something's 90% slower, yes, it's worth keeping in mind, but it's really not until you start get magnitudes-of-order slower (10x, 100x, 1000x) that alarm bells should really go off.  And if I ever do need that last millisecond of performance?  Well then I'll optimize JUST THAT problem spot.  To me it's worth it for the readability, speed-to-market, and maintainability.

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  • Trouble with copying dictionaries and using deepcopy on an SQLAlchemy ORM object

    - by Az
    Hi there, I'm doing a Simulated Annealing algorithm to optimise a given allocation of students and projects. This is language-agnostic pseudocode from Wikipedia: s ? s0; e ? E(s) // Initial state, energy. sbest ? s; ebest ? e // Initial "best" solution k ? 0 // Energy evaluation count. while k < kmax and e > emax // While time left & not good enough: snew ? neighbour(s) // Pick some neighbour. enew ? E(snew) // Compute its energy. if enew < ebest then // Is this a new best? sbest ? snew; ebest ? enew // Save 'new neighbour' to 'best found'. if P(e, enew, temp(k/kmax)) > random() then // Should we move to it? s ? snew; e ? enew // Yes, change state. k ? k + 1 // One more evaluation done return sbest // Return the best solution found. The following is an adaptation of the technique. My supervisor said the idea is fine in theory. First I pick up some allocation (i.e. an entire dictionary of students and their allocated projects, including the ranks for the projects) from entire set of randomised allocations, copy it and pass it to my function. Let's call this allocation aOld (it is a dictionary). aOld has a weight related to it called wOld. The weighting is described below. The function does the following: Let this allocation, aOld be the best_node From all the students, pick a random number of students and stick in a list Strip (DEALLOCATE) them of their projects ++ reflect the changes for projects (allocated parameter is now False) and lecturers (free up slots if one or more of their projects are no longer allocated) Randomise that list Try assigning (REALLOCATE) everyone in that list projects again Calculate the weight (add up ranks, rank 1 = 1, rank 2 = 2... and no project rank = 101) For this new allocation aNew, if the weight wNew is smaller than the allocation weight wOld I picked up at the beginning, then this is the best_node (as defined by the Simulated Annealing algorithm above). Apply the algorithm to aNew and continue. If wOld < wNew, then apply the algorithm to aOld again and continue. The allocations/data-points are expressed as "nodes" such that a node = (weight, allocation_dict, projects_dict, lecturers_dict) Right now, I can only perform this algorithm once, but I'll need to try for a number N (denoted by kmax in the Wikipedia snippet) and make sure I always have with me, the previous node and the best_node. So that I don't modify my original dictionaries (which I might want to reset to), I've done a shallow copy of the dictionaries. From what I've read in the docs, it seems that it only copies the references and since my dictionaries contain objects, changing the copied dictionary ends up changing the objects anyway. So I tried to use copy.deepcopy().These dictionaries refer to objects that have been mapped with SQLA. Questions: I've been given some solutions to the problems faced but due to my über green-ness with using Python, they all sound rather cryptic to me. Deepcopy isn't playing nicely with SQLA. I've been told thatdeepcopy on ORM objects probably has issues that prevent it from working as you'd expect. Apparently I'd be better off "building copy constructors, i.e. def copy(self): return FooBar(....)." Can someone please explain what that means? I checked and found out that deepcopy has issues because SQLAlchemy places extra information on your objects, i.e. an _sa_instance_state attribute, that I wouldn't want in the copy but is necessary for the object to have. I've been told: "There are ways to manually blow away the old _sa_instance_state and put a new one on the object, but the most straightforward is to make a new object with __init__() and set up the attributes that are significant, instead of doing a full deep copy." What exactly does that mean? Do I create a new, unmapped class similar to the old, mapped one? An alternate solution is that I'd have to "implement __deepcopy__() on your objects and ensure that a new _sa_instance_state is set up, there are functions in sqlalchemy.orm.attributes which can help with that." Once again this is beyond me so could someone kindly explain what it means? A more general question: given the above information are there any suggestions on how I can maintain the information/state for the best_node (which must always persist through my while loop) and the previous_node, if my actual objects (referenced by the dictionaries, therefore the nodes) are changing due to the deallocation/reallocation taking place? That is, without using copy?

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  • Online ALTER TABLE in MySQL 5.6

    - by Marko Mäkelä
    This is the low-level view of data dictionary language (DDL) operations in the InnoDB storage engine in MySQL 5.6. John Russell gave a more high-level view in his blog post April 2012 Labs Release – Online DDL Improvements. MySQL before the InnoDB Plugin Traditionally, the MySQL storage engine interface has taken a minimalistic approach to data definition language. The only natively supported operations were CREATE TABLE, DROP TABLE and RENAME TABLE. Consider the following example: CREATE TABLE t(a INT); INSERT INTO t VALUES (1),(2),(3); CREATE INDEX a ON t(a); DROP TABLE t; The CREATE INDEX statement would be executed roughly as follows: CREATE TABLE temp(a INT, INDEX(a)); INSERT INTO temp SELECT * FROM t; RENAME TABLE t TO temp2; RENAME TABLE temp TO t; DROP TABLE temp2; You could imagine that the database could crash when copying all rows from the original table to the new one. For example, it could run out of file space. Then, on restart, InnoDB would roll back the huge INSERT transaction. To fix things a little, a hack was added to ha_innobase::write_row for committing the transaction every 10,000 rows. Still, it was frustrating that even a simple DROP INDEX would make the table unavailable for modifications for a long time. Fast Index Creation in the InnoDB Plugin of MySQL 5.1 MySQL 5.1 introduced a new interface for CREATE INDEX and DROP INDEX. The old table-copying approach can still be forced by SET old_alter_table=0. This interface is used in MySQL 5.5 and in the InnoDB Plugin for MySQL 5.1. Apart from the ability to do a quick DROP INDEX, the main advantage is that InnoDB will execute a merge-sort algorithm before inserting the index records into each index that is being created. This should speed up the insert into the secondary index B-trees and potentially result in a better B-tree fill factor. The 5.1 ALTER TABLE interface was not perfect. For example, DROP FOREIGN KEY still invoked the table copy. Renaming columns could conflict with InnoDB foreign key constraints. Combining ADD KEY and DROP KEY in ALTER TABLE was problematic and not atomic inside the storage engine. The ALTER TABLE interface in MySQL 5.6 The ALTER TABLE storage engine interface was completely rewritten in MySQL 5.6. Instead of introducing a method call for every conceivable operation, MySQL 5.6 introduced a handful of methods, and data structures that keep track of the requested changes. In MySQL 5.6, online ALTER TABLE operation can be requested by specifying LOCK=NONE. Also LOCK=SHARED and LOCK=EXCLUSIVE are available. The old-style table copying can be requested by ALGORITHM=COPY. That one will require at least LOCK=SHARED. From the InnoDB point of view, anything that is possible with LOCK=EXCLUSIVE is also possible with LOCK=SHARED. Most ALGORITHM=INPLACE operations inside InnoDB can be executed online (LOCK=NONE). InnoDB will always require an exclusive table lock in two phases of the operation. The execution phases are tied to a number of methods: handler::check_if_supported_inplace_alter Checks if the storage engine can perform all requested operations, and if so, what kind of locking is needed. handler::prepare_inplace_alter_table InnoDB uses this method to set up the data dictionary cache for upcoming CREATE INDEX operation. We need stubs for the new indexes, so that we can keep track of changes to the table during online index creation. Also, crash recovery would drop any indexes that were incomplete at the time of the crash. handler::inplace_alter_table In InnoDB, this method is used for creating secondary indexes or for rebuilding the table. This is the ‘main’ phase that can be executed online (with concurrent writes to the table). handler::commit_inplace_alter_table This is where the operation is committed or rolled back. Here, InnoDB would drop any indexes, rename any columns, drop or add foreign keys, and finalize a table rebuild or index creation. It would also discard any logs that were set up for online index creation or table rebuild. The prepare and commit phases require an exclusive lock, blocking all access to the table. If MySQL times out while upgrading the table meta-data lock for the commit phase, it will roll back the ALTER TABLE operation. In MySQL 5.6, data definition language operations are still not fully atomic, because the data dictionary is split. Part of it is inside InnoDB data dictionary tables. Part of the information is only available in the *.frm file, which is not covered by any crash recovery log. But, there is a single commit phase inside the storage engine. Online Secondary Index Creation It may occur that an index needs to be created on a new column to speed up queries. But, it may be unacceptable to block modifications on the table while creating the index. It turns out that it is conceptually not so hard to support online index creation. All we need is some more execution phases: Set up a stub for the index, for logging changes. Scan the table for index records. Sort the index records. Bulk load the index records. Apply the logged changes. Replace the stub with the actual index. Threads that modify the table will log the operations to the logs of each index that is being created. Errors, such as log overflow or uniqueness violations, will only be flagged by the ALTER TABLE thread. The log is conceptually similar to the InnoDB change buffer. The bulk load of index records will bypass record locking. We still generate redo log for writing the index pages. It would suffice to log page allocations only, and to flush the index pages from the buffer pool to the file system upon completion. Native ALTER TABLE Starting with MySQL 5.6, InnoDB supports most ALTER TABLE operations natively. The notable exceptions are changes to the column type, ADD FOREIGN KEY except when foreign_key_checks=0, and changes to tables that contain FULLTEXT indexes. The keyword ALGORITHM=INPLACE is somewhat misleading, because certain operations cannot be performed in-place. For example, changing the ROW_FORMAT of a table requires a rebuild. Online operation (LOCK=NONE) is not allowed in the following cases: when adding an AUTO_INCREMENT column, when the table contains FULLTEXT indexes or a hidden FTS_DOC_ID column, or when there are FOREIGN KEY constraints referring to the table, with ON…CASCADE or ON…SET NULL option. The FOREIGN KEY limitations are needed, because MySQL does not acquire meta-data locks on the child or parent tables when executing SQL statements. Theoretically, InnoDB could support operations like ADD COLUMN and DROP COLUMN in-place, by lazily converting the table to a newer format. This would require that the data dictionary keep multiple versions of the table definition. For simplicity, we will copy the entire table, even for DROP COLUMN. The bulk copying of the table will bypass record locking and undo logging. For facilitating online operation, a temporary log will be associated with the clustered index of table. Threads that modify the table will also write the changes to the log. When altering the table, we skip all records that have been marked for deletion. In this way, we can simply discard any undo log records that were not yet purged from the original table. Off-page columns, or BLOBs, are an important consideration. We suspend the purge of delete-marked records if it would free any off-page columns from the old table. This is because the BLOBs can be needed when applying changes from the log. We have special logging for handling the ROLLBACK of an INSERT that inserted new off-page columns. This is because the columns will be freed at rollback.

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 4

    - by MarkPearl
    Learning Outcomes Explain the characteristics of memory systems Describe the memory hierarchy Discuss cache memory principles Discuss issues relevant to cache design Describe the cache organization of the Pentium Computer Memory Systems There are key characteristics of memory… Location – internal or external Capacity – expressed in terms of bytes Unit of Transfer – the number of bits read out of or written into memory at a time Access Method – sequential, direct, random or associative From a users perspective the two most important characteristics of memory are… Capacity Performance – access time, memory cycle time, transfer rate The trade off for memory happens along three axis… Faster access time, greater cost per bit Greater capacity, smaller cost per bit Greater capacity, slower access time This leads to people using a tiered approach in their use of memory   As one goes down the hierarchy, the following occurs… Decreasing cost per bit Increasing capacity Increasing access time Decreasing frequency of access of the memory by the processor The use of two levels of memory to reduce average access time works in principle, but only if conditions 1 to 4 apply. A variety of technologies exist that allow us to accomplish this. Thus it is possible to organize data across the hierarchy such that the percentage of accesses to each successively lower level is substantially less than that of the level above. A portion of main memory can be used as a buffer to hold data temporarily that is to be read out to disk. This is sometimes referred to as a disk cache and improves performance in two ways… Disk writes are clustered. Instead of many small transfers of data, we have a few large transfers of data. This improves disk performance and minimizes processor involvement. Some data designed for write-out may be referenced by a program before the next dump to disk. In that case the data is retrieved rapidly from the software cache rather than slowly from disk. Cache Memory Principles Cache memory is substantially faster than main memory. A caching system works as follows.. When a processor attempts to read a word of memory, a check is made to see if this in in cache memory… If it is, the data is supplied, If it is not in the cache, a block of main memory, consisting of a fixed number of words is loaded to the cache. Because of the phenomenon of locality of references, when a block of data is fetched into the cache, it is likely that there will be future references to that same memory location or to other words in the block. Elements of Cache Design While there are a large number of cache implementations, there are a few basic design elements that serve to classify and differentiate cache architectures… Cache Addresses Cache Size Mapping Function Replacement Algorithm Write Policy Line Size Number of Caches Cache Addresses Almost all non-embedded processors support virtual memory. Virtual memory in essence allows a program to address memory from a logical point of view without needing to worry about the amount of physical memory available. When virtual addresses are used the designer may choose to place the cache between the MMU (memory management unit) and the processor or between the MMU and main memory. The disadvantage of virtual memory is that most virtual memory systems supply each application with the same virtual memory address space (each application sees virtual memory starting at memory address 0), which means the cache memory must be completely flushed with each application context switch or extra bits must be added to each line of the cache to identify which virtual address space the address refers to. Cache Size We would like the size of the cache to be small enough so that the overall average cost per bit is close to that of main memory alone and large enough so that the overall average access time is close to that of the cache alone. Also, larger caches are slightly slower than smaller ones. Mapping Function Because there are fewer cache lines than main memory blocks, an algorithm is needed for mapping main memory blocks into cache lines. The choice of mapping function dictates how the cache is organized. Three techniques can be used… Direct – simplest technique, maps each block of main memory into only one possible cache line Associative – Each main memory block to be loaded into any line of the cache Set Associative – exhibits the strengths of both the direct and associative approaches while reducing their disadvantages For detailed explanations of each approach – read the text book (page 148 – 154) Replacement Algorithm For associative and set associating mapping a replacement algorithm is needed to determine which of the existing blocks in the cache must be replaced by a new block. There are four common approaches… LRU (Least recently used) FIFO (First in first out) LFU (Least frequently used) Random selection Write Policy When a block resident in the cache is to be replaced, there are two cases to consider If no writes to that block have happened in the cache – discard it If a write has occurred, a process needs to be initiated where the changes in the cache are propagated back to the main memory. There are several approaches to achieve this including… Write Through – all writes to the cache are done to the main memory as well at the point of the change Write Back – when a block is replaced, all dirty bits are written back to main memory The problem is complicated when we have multiple caches, there are techniques to accommodate for this but I have not summarized them. Line Size When a block of data is retrieved and placed in the cache, not only the desired word but also some number of adjacent words are retrieved. As the block size increases from very small to larger sizes, the hit ratio will at first increase because of the principle of locality, which states that the data in the vicinity of a referenced word are likely to be referenced in the near future. As the block size increases, more useful data are brought into cache. The hit ratio will begin to decrease as the block becomes even bigger and the probability of using the newly fetched information becomes less than the probability of using the newly fetched information that has to be replaced. Two specific effects come into play… Larger blocks reduce the number of blocks that fit into a cache. Because each block fetch overwrites older cache contents, a small number of blocks results in data being overwritten shortly after they are fetched. As a block becomes larger, each additional word is farther from the requested word and therefore less likely to be needed in the near future. The relationship between block size and hit ratio is complex, and no set approach is judged to be the best in all circumstances.   Pentium 4 and ARM cache organizations The processor core consists of four major components: Fetch/decode unit – fetches program instruction in order from the L2 cache, decodes these into a series of micro-operations, and stores the results in the L2 instruction cache Out-of-order execution logic – Schedules execution of the micro-operations subject to data dependencies and resource availability – thus micro-operations may be scheduled for execution in a different order than they were fetched from the instruction stream. As time permits, this unit schedules speculative execution of micro-operations that may be required in the future Execution units – These units execute micro-operations, fetching the required data from the L1 data cache and temporarily storing results in registers Memory subsystem – This unit includes the L2 and L3 caches and the system bus, which is used to access main memory when the L1 and L2 caches have a cache miss and to access the system I/O resources

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  • Quartz.Net Writing your first Hello World Job

    - by Tarun Arora
    In this blog post I’ll be covering, 01: A few things to consider before you should schedule a Job using Quartz.Net 02: Setting up your solution to use Quartz.Net API 03: Quartz.Net configuration 04: Writing & scheduling a hello world job with Quartz.Net If you are new to Quartz.Net I would recommend going through, A brief introduction to Quartz.net Walkthrough of Installing & Testing Quartz.Net as a Windows Service A few things to consider before you should schedule a Job using Quartz.Net - An instance of the scheduler service - A trigger - And last but not the least a job For example, if I wanted to schedule a script to run on the server, I should be jotting down answers to the below questions, a. Considering there are multiple machines set up with Quartz.Net windows service, how can I choose the instance of Quartz.Net where I want my script to be run b. What will trigger the execution of the job c. How often do I want the job to run d. Do I want the job to run right away or start after a delay or may be have the job start at a specific time e. What will happen to my job if Quartz.Net windows service is reset f. Do I want multiple instances of this job to run concurrently g. Can I pass parameters to the job being executed by Quartz.Net windows service Setting up your solution to use Quartz.Net API 1. Create a new C# Console Application project and call it “HelloWorldQuartzDotNet” and add a reference to Quartz.Net.dll. I use the NuGet Package Manager to add the reference. This can be done by right clicking references and choosing Manage NuGet packages, from the Nuget Package Manager choose Online from the left panel and in the search box on the right search for Quartz.Net. Click Install on the package “Quartz” (Screen shot below). 2. Right click the project and choose Add New Item. Add a new Interface and call it ‘IScheduledJob.cs’. Mark the Interface public and add the signature for Run. Your interface should look like below. namespace HelloWorldQuartzDotNet { public interface IScheduledJob { void Run(); } }   3. Right click the project and choose Add new Item. Add a class and call it ‘Scheduled Job’. Use this class to implement the interface ‘IscheduledJob.cs’. Look at the pseudo code in the implementation of the Run method. using System; namespace HelloWorldQuartzDotNet { class ScheduledJob : IScheduledJob { public void Run() { // Get an instance of the Quartz.Net scheduler // Define the Job to be scheduled // Associate a trigger with the Job // Assign the Job to the scheduler throw new NotImplementedException(); } } }   I’ll get into the implementation in more detail, but let’s look at the minimal configuration a sample configuration file for Quartz.Net service to work. Quartz.Net configuration In the App.Config file copy the below configuration <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="quartz" type="System.Configuration.NameValueSectionHandler, System, Version=1.0.5000.0,Culture=neutral, PublicKeyToken=b77a5c561934e089" /> </configSections> <quartz> <add key="quartz.scheduler.instanceName" value="ServerScheduler" /> <add key="quartz.threadPool.type" value="Quartz.Simpl.SimpleThreadPool, Quartz" /> <add key="quartz.threadPool.threadCount" value="10" /> <add key="quartz.threadPool.threadPriority" value="2" /> <add key="quartz.jobStore.misfireThreshold" value="60000" /> <add key="quartz.jobStore.type" value="Quartz.Simpl.RAMJobStore, Quartz" /> </quartz> </configuration>   As you can see in the configuration above, I have included the instance name of the quartz scheduler, the thread pool type, count and priority, the job store type has been defined as RAM. You have the option of configuring that to ADO.NET JOB store. More details here. Writing & scheduling a hello world job with Quartz.Net Once fully implemented the ScheduleJob.cs class should look like below. I’ll walk you through the details of the implementation… - GetScheduler() uses the name of the quartz.net and listens on localhost port 555 to try and connect to the quartz.net windows service. - Run() an attempt is made to start the scheduler in case it is in standby mode - I have defined a job “WriteHelloToConsole” (that’s the name of the job), this job belongs to the group “IT”. Think of group as a logical grouping feature. It helps you bucket jobs into groups. Quartz.Net gives you the ability to pause or delete all jobs in a group (We’ll look at that in some of the future posts). I have requested for recovery of this job in case the quartz.net service fails over to the other node in the cluster. The jobType is “HelloWorldJob”. This is the class that would be called to execute the job. More details on this below… - I have defined a trigger for my job. I have called the trigger “WriteHelloToConsole”. The Trigger works on the cron schedule “0 0/1 * 1/1 * ? *” which means fire the job once every minute. I would recommend that you look at www.cronmaker.com a free and great website to build and parse cron expressions. The trigger has a priority 1. So, if two jobs are run at the same time, this trigger will have high priority and will be run first. - Use the Job and Trigger to schedule the job. This method returns a datetime offeset. It is possible to see the next fire time for the job from this variable. using System.Collections.Specialized; using System.Configuration; using Quartz; using System; using Quartz.Impl; namespace HelloWorldQuartzDotNet { class ScheduledJob : IScheduledJob { public void Run() { // Get an instance of the Quartz.Net scheduler var schd = GetScheduler(); // Start the scheduler if its in standby if (!schd.IsStarted) schd.Start(); // Define the Job to be scheduled var job = JobBuilder.Create<HelloWorldJob>() .WithIdentity("WriteHelloToConsole", "IT") .RequestRecovery() .Build(); // Associate a trigger with the Job var trigger = (ICronTrigger)TriggerBuilder.Create() .WithIdentity("WriteHelloToConsole", "IT") .WithCronSchedule("0 0/1 * 1/1 * ? *") // visit http://www.cronmaker.com/ Queues the job every minute .WithPriority(1) .Build(); // Assign the Job to the scheduler var schedule = schd.ScheduleJob(job, trigger); Console.WriteLine("Job '{0}' scheduled for '{1}'", "", schedule.ToString("r")); } // Get an instance of the Quartz.Net scheduler private static IScheduler GetScheduler() { try { var properties = new NameValueCollection(); properties["quartz.scheduler.instanceName"] = "ServerScheduler"; // set remoting expoter properties["quartz.scheduler.proxy"] = "true"; properties["quartz.scheduler.proxy.address"] = string.Format("tcp://{0}:{1}/{2}", "localhost", "555", "QuartzScheduler"); // Get a reference to the scheduler var sf = new StdSchedulerFactory(properties); return sf.GetScheduler(); } catch (Exception ex) { Console.WriteLine("Scheduler not available: '{0}'", ex.Message); throw; } } } }   The above highlighted values have been taken from the Quartz.config file, this file is available in the Quartz.net server installation directory. Implementation of my HelloWorldJob Class below. The HelloWorldJob class gets called to execute the job “WriteHelloToConsole” using the once every minute trigger set up for this job. The HelloWorldJob is a class that implements the interface IJob. I’ll walk you through the details of the implementation… - context is passed to the method execute by the quartz.net scheduler service. This has everything you need to pull out the job, trigger specific information. - for example. I have pulled out the value of the jobKey name, the fire time and next fire time. using Quartz; using System; namespace HelloWorldQuartzDotNet { class HelloWorldJob : IJob { public void Execute(IJobExecutionContext context) { try { Console.WriteLine("Job {0} fired @ {1} next scheduled for {2}", context.JobDetail.Key, context.FireTimeUtc.Value.ToString("r"), context.NextFireTimeUtc.Value.ToString("r")); Console.WriteLine("Hello World!"); } catch (Exception ex) { Console.WriteLine("Failed: {0}", ex.Message); } } } }   I’ll add a call to call the scheduler in the Main method in Program.cs using System; using System.Threading; namespace HelloWorldQuartzDotNet { class Program { static void Main(string[] args) { try { var sj = new ScheduledJob(); sj.Run(); Thread.Sleep(10000 * 10000); } catch (Exception ex) { Console.WriteLine("Failed: {0}", ex.Message); } } } }   This was third in the series of posts on enterprise scheduling using Quartz.net, in the next post I’ll be covering how to pass parameters to the scheduled task scheduled on Quartz.net windows service. Thank you for taking the time out and reading this blog post. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Stay tuned!

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  • Am I right about the differences between Floyd-Warshall, Dijkstra's and Bellman-Ford algorithms?

    - by Programming Noob
    I've been studying the three and I'm stating my inferences from them below. Could someone tell me if I have understood them accurately enough or not? Thank you. Dijkstra's algorithm is used only when you have a single source and you want to know the smallest path from one node to another, but fails in cases like this Floyd-Warshall's algorithm is used when any of all the nodes can be a source, so you want the shortest distance to reach any destination node from any source node. This only fails when there are negative cycles (this is the most important one. I mean, this is the one I'm least sure about:) 3.Bellman-Ford is used like Dijkstra's, when there is only one source. This can handle negative weights and its working is the same as Floyd-Warshall's except for one source, right? If you need to have a look, the corresponding algorithms are (courtesy Wikipedia): Bellman-Ford: procedure BellmanFord(list vertices, list edges, vertex source) // This implementation takes in a graph, represented as lists of vertices // and edges, and modifies the vertices so that their distance and // predecessor attributes store the shortest paths. // Step 1: initialize graph for each vertex v in vertices: if v is source then v.distance := 0 else v.distance := infinity v.predecessor := null // Step 2: relax edges repeatedly for i from 1 to size(vertices)-1: for each edge uv in edges: // uv is the edge from u to v u := uv.source v := uv.destination if u.distance + uv.weight < v.distance: v.distance := u.distance + uv.weight v.predecessor := u // Step 3: check for negative-weight cycles for each edge uv in edges: u := uv.source v := uv.destination if u.distance + uv.weight < v.distance: error "Graph contains a negative-weight cycle" Dijkstra: 1 function Dijkstra(Graph, source): 2 for each vertex v in Graph: // Initializations 3 dist[v] := infinity ; // Unknown distance function from 4 // source to v 5 previous[v] := undefined ; // Previous node in optimal path 6 // from source 7 8 dist[source] := 0 ; // Distance from source to source 9 Q := the set of all nodes in Graph ; // All nodes in the graph are 10 // unoptimized - thus are in Q 11 while Q is not empty: // The main loop 12 u := vertex in Q with smallest distance in dist[] ; // Start node in first case 13 if dist[u] = infinity: 14 break ; // all remaining vertices are 15 // inaccessible from source 16 17 remove u from Q ; 18 for each neighbor v of u: // where v has not yet been 19 removed from Q. 20 alt := dist[u] + dist_between(u, v) ; 21 if alt < dist[v]: // Relax (u,v,a) 22 dist[v] := alt ; 23 previous[v] := u ; 24 decrease-key v in Q; // Reorder v in the Queue 25 return dist; Floyd-Warshall: 1 /* Assume a function edgeCost(i,j) which returns the cost of the edge from i to j 2 (infinity if there is none). 3 Also assume that n is the number of vertices and edgeCost(i,i) = 0 4 */ 5 6 int path[][]; 7 /* A 2-dimensional matrix. At each step in the algorithm, path[i][j] is the shortest path 8 from i to j using intermediate vertices (1..k-1). Each path[i][j] is initialized to 9 edgeCost(i,j). 10 */ 11 12 procedure FloydWarshall () 13 for k := 1 to n 14 for i := 1 to n 15 for j := 1 to n 16 path[i][j] = min ( path[i][j], path[i][k]+path[k][j] );

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  • F# and the rose-tinted reflection

    - by CliveT
    We're already seeing increasing use of many cores on client desktops. It is a change that has been long predicted. It is not just a change in architecture, but our notions of efficiency in a program. No longer can we focus on the asymptotic complexity of an algorithm by counting the steps that a single core processor would take to execute it. Instead we'll soon be more concerned about the scalability of the algorithm and how well we can increase the performance as we increase the number of cores. This may even lead us to throw away our most efficient algorithms, and switch to less efficient algorithms that scale better. We might even be willing to waste cycles in order to speculatively execute at the algorithm rather than the hardware level. State is the big headache in this parallel world. At the hardware level, main memory doesn't necessarily contain the definitive value corresponding to a particular address. An update to a location might still be held in a CPU's local cache and it might be some time before the value gets propagated. To get the latest value, and the notion of "latest" takes a lot of defining in this world of rapidly mutating state, the CPUs may well need to communicate to decide who has the definitive value of a particular address in order to avoid lost updates. At the user program level, this means programmers will need to lock objects before modifying them, or attempt to avoid the overhead of locking by understanding the memory models at a very deep level. I think it's this need to avoid statefulness that has led to the recent resurgence of interest in functional languages. In the 1980s, functional languages started getting traction when research was carried out into how programs in such languages could be auto-parallelised. Sadly, the impracticality of some of the languages, the overheads of communication during this parallel execution, and rapid improvements in compiler technology on stock hardware meant that the functional languages fell by the wayside. The one thing that these languages were good at was getting rid of implicit state, and this single idea seems like a solution to the problems we are going to face in the coming years. Whether these languages will catch on is hard to predict. The mindset for writing a program in a functional language is really very different from the way that object-oriented problem decomposition happens - one has to focus on the verbs instead of the nouns, which takes some getting used to. There are a number of hybrid functional/object languages that have been becoming more popular in recent times. These half-way houses make it easy to use functional ideas for some parts of the program while still allowing access to the underlying object-focused platform without a great deal of impedance mismatch. One example is F# running on the CLR which, in Visual Studio 2010, has because a first class member of the pack. Inside Visual Studio 2010, the tooling for F# has improved to the point where it is easy to set breakpoints and watch values change while debugging at the source level. In my opinion, it is the tooling support that will enable the widespread adoption of functional languages - without this support, people will put off any transition into the functional world for as long as they possibly can. Without tool support it will make it hard to learn these languages. One tool that doesn't currently support F# is Reflector. The idea of decompiling IL to a functional language is daunting, but F# is potentially so important I couldn't dismiss the idea. As I'm currently developing Reflector 6.5, I thought it wise to take four days just to see how far I could get in doing so, even if it achieved little more than to be clearer on how much was possible, and how long it might take. You can read what happened here, and of the insights it gave us on ways to improve the tool.

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  • Speeding up procedural texture generation

    - by FalconNL
    Recently I've begun working on a game that takes place in a procedurally generated solar system. After a bit of a learning curve (having neither worked with Scala, OpenGL 2 ES or Libgdx before), I have a basic tech demo going where you spin around a single procedurally textured planet: The problem I'm running into is the performance of the texture generation. A quick overview of what I'm doing: a planet is a cube that has been deformed to a sphere. To each side, a n x n (e.g. 256 x 256) texture is applied, which are bundled in one 8n x n texture that is sent to the fragment shader. The last two spaces are not used, they're only there to make sure the width is a power of 2. The texture is currently generated on the CPU, using the updated 2012 version of the simplex noise algorithm linked to in the paper 'Simplex noise demystified'. The scene I'm using to test the algorithm contains two spheres: the planet and the background. Both use a greyscale texture consisting of six octaves of 3D simplex noise, so for example if we choose 128x128 as the texture size there are 128 x 128 x 6 x 2 x 6 = about 1.2 million calls to the noise function. The closest you will get to the planet is about what's shown in the screenshot and since the game's target resolution is 1280x720 that means I'd prefer to use 512x512 textures. Combine that with the fact the actual textures will of course be more complicated than basic noise (There will be a day and night texture, blended in the fragment shader based on sunlight, and a specular mask. I need noise for continents, terrain color variation, clouds, city lights, etc.) and we're looking at something like 512 x 512 x 6 x 3 x 15 = 70 million noise calls for the planet alone. In the final game, there will be activities when traveling between planets, so a wait of 5 or 10 seconds, possibly 20, would be acceptable since I can calculate the texture in the background while traveling, though obviously the faster the better. Getting back to our test scene, performance on my PC isn't too terrible, though still too slow considering the final result is going to be about 60 times worse: 128x128 : 0.1s 256x256 : 0.4s 512x512 : 1.7s This is after I moved all performance-critical code to Java, since trying to do so in Scala was a lot worse. Running this on my phone (a Samsung Galaxy S3), however, produces a more problematic result: 128x128 : 2s 256x256 : 7s 512x512 : 29s Already far too long, and that's not even factoring in the fact that it'll be minutes instead of seconds in the final version. Clearly something needs to be done. Personally, I see a few potential avenues, though I'm not particularly keen on any of them yet: Don't precalculate the textures, but let the fragment shader calculate everything. Probably not feasible, because at one point I had the background as a fullscreen quad with a pixel shader and I got about 1 fps on my phone. Use the GPU to render the texture once, store it and use the stored texture from then on. Upside: might be faster than doing it on the CPU since the GPU is supposed to be faster at floating point calculations. Downside: effects that cannot (easily) be expressed as functions of simplex noise (e.g. gas planet vortices, moon craters, etc.) are a lot more difficult to code in GLSL than in Scala/Java. Calculate a large amount of noise textures and ship them with the application. I'd like to avoid this if at all possible. Lower the resolution. Buys me a 4x performance gain, which isn't really enough plus I lose a lot of quality. Find a faster noise algorithm. If anyone has one I'm all ears, but simplex is already supposed to be faster than perlin. Adopt a pixel art style, allowing for lower resolution textures and fewer noise octaves. While I originally envisioned the game in this style, I've come to prefer the realistic approach. I'm doing something wrong and the performance should already be one or two orders of magnitude better. If this is the case, please let me know. If anyone has any suggestions, tips, workarounds, or other comments regarding this problem I'd love to hear them.

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  • Fastest pathfinding for static node matrix

    - by Sean Martin
    I'm programming a route finding routine in VB.NET for an online game I play, and I'm searching for the fastest route finding algorithm for my map type. The game takes place in space, with thousands of solar systems connected by jump gates. The game devs have provided a DB dump containing a list of every system and the systems it can jump to. The map isn't quite a node tree, since some branches can jump to other branches - more of a matrix. What I need is a fast pathfinding algorithm. I have already implemented an A* routine and a Dijkstra's, both find the best path but are too slow for my purposes - a search that considers about 5000 nodes takes over 20 seconds to compute. A similar program on a website can do the same search in less than a second. This website claims to use D*, which I have looked into. That algorithm seems more appropriate for dynamic maps rather than one that does not change - unless I misunderstand it's premise. So is there something faster I can use for a map that is not your typical tile/polygon base? GBFS? Perhaps a DFS? Or have I likely got some problem with my A* - maybe poorly chosen heuristics or movement cost? Currently my movement cost is the length of the jump (the DB dump has solar system coordinates as well), and the heuristic is a quick euclidean calculation from the node to the goal. In case anyone has some optimizations for my A*, here is the routine that consumes about 60% of my processing time, according to my profiler. The coordinateData table contains a list of every system's coordinates, and neighborNode.distance is the distance of the jump. Private Function findDistance(ByVal startSystem As Integer, ByVal endSystem As Integer) As Integer 'hCount += 1 'If hCount Mod 0 = 0 Then 'Return hCache 'End If 'Initialize variables to be filled Dim x1, x2, y1, y2, z1, z2 As Integer 'LINQ queries for solar system data Dim systemFromData = From result In jumpDataDB.coordinateDatas Where result.systemId = startSystem Select result.x, result.y, result.z Dim systemToData = From result In jumpDataDB.coordinateDatas Where result.systemId = endSystem Select result.x, result.y, result.z 'LINQ execute 'Fill variables with solar system data for from and to system For Each solarSystem In systemFromData x1 = (solarSystem.x) y1 = (solarSystem.y) z1 = (solarSystem.z) Next For Each solarSystem In systemToData x2 = (solarSystem.x) y2 = (solarSystem.y) z2 = (solarSystem.z) Next Dim x3 = Math.Abs(x1 - x2) Dim y3 = Math.Abs(y1 - y2) Dim z3 = Math.Abs(z1 - z2) 'Calculate distance and round 'Dim distance = Math.Round(Math.Sqrt(Math.Abs((x1 - x2) ^ 2) + Math.Abs((y1 - y2) ^ 2) + Math.Abs((z1 - z2) ^ 2))) Dim distance = firstConstant * Math.Min(secondConstant * (x3 + y3 + z3), Math.Max(x3, Math.Max(y3, z3))) 'Dim distance = Math.Abs(x1 - x2) + Math.Abs(z1 - z2) + Math.Abs(y1 - y2) 'hCache = distance Return distance End Function And the main loop, the other 30% 'Begin search While openList.Count() != 0 'Set current system and move node to closed currentNode = lowestF() move(currentNode.id) For Each neighborNode In neighborNodes If Not onList(neighborNode.toSystem, 0) Then If Not onList(neighborNode.toSystem, 1) Then Dim newNode As New nodeData() newNode.id = neighborNode.toSystem newNode.parent = currentNode.id newNode.g = currentNode.g + neighborNode.distance newNode.h = findDistance(newNode.id, endSystem) newNode.f = newNode.g + newNode.h newNode.security = neighborNode.security openList.Add(newNode) shortOpenList(OLindex) = newNode.id OLindex += 1 Else Dim proposedG As Integer = currentNode.g + neighborNode.distance If proposedG < gValue(neighborNode.toSystem) Then changeParent(neighborNode.toSystem, currentNode.id, proposedG) End If End If End If Next 'Check to see if done If currentNode.id = endSystem Then Exit While End If End While If clarification is needed on my spaghetti code, I'll try to explain.

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  • Skewed: a rotating camera in a simple CPU-based voxel raycaster/raytracer

    - by voxelizr
    TL;DR -- in my first simple software voxel raycaster, I cannot get camera rotations to work, seemingly correct matrices notwithstanding. The result is skewed: like a flat rendering, correctly rotated, however distorted and without depth. (While axis-aligned ie. unrotated, depth and parallax are as expected.) I'm trying to write a simple voxel raycaster as a learning exercise. This is purely CPU based for now until I figure out how things work exactly -- fow now, OpenGL is just (ab)used to blit the generated bitmap to the screen as often as possible. Now I have gotten to the point where a perspective-projection camera can move through the world and I can render (mostly, minus some artifacts that need investigation) perspective-correct 3-dimensional views of the "world", which is basically empty but contains a voxel cube of the Stanford Bunny. So I have a camera that I can move up and down, strafe left and right and "walk forward/backward" -- all axis-aligned so far, no camera rotations. Herein lies my problem. Screenshot #1: correct depth when the camera is still strictly axis-aligned, ie. un-rotated. Now I have for a few days been trying to get rotation to work. The basic logic and theory behind matrices and 3D rotations, in theory, is very clear to me. Yet I have only ever achieved a "2.5 rendering" when the camera rotates... fish-eyey, bit like in Google Streetview: even though I have a volumetric world representation, it seems --no matter what I try-- like I would first create a rendering from the "front view", then rotate that flat rendering according to camera rotation. Needless to say, I'm by now aware that rotating rays is not particularly necessary and error-prone. Still, in my most recent setup, with the most simplified raycast ray-position-and-direction algorithm possible, my rotation still produces the same fish-eyey flat-render-rotated style looks: Screenshot #2: camera "rotated to the right by 39 degrees" -- note how the blue-shaded left-hand side of the cube from screen #2 is not visible in this rotation, yet by now "it really should"! Now of course I'm aware of this: in a simple axis-aligned-no-rotation-setup like I had in the beginning, the ray simply traverses in small steps the positive z-direction, diverging to the left or right and top or bottom only depending on pixel position and projection matrix. As I "rotate the camera to the right or left" -- ie I rotate it around the Y-axis -- those very steps should be simply transformed by the proper rotation matrix, right? So for forward-traversal the Z-step gets a bit smaller the more the cam rotates, offset by an "increase" in the X-step. Yet for the pixel-position-based horizontal+vertical-divergence, increasing fractions of the x-step need to be "added" to the z-step. Somehow, none of my many matrices that I experimented with, nor my experiments with matrix-less hardcoded verbose sin/cos calculations really get this part right. Here's my basic per-ray pre-traversal algorithm -- syntax in Go, but take it as pseudocode: fx and fy: pixel positions x and y rayPos: vec3 for the ray starting position in world-space (calculated as below) rayDir: vec3 for the xyz-steps to be added to rayPos in each step during ray traversal rayStep: a temporary vec3 camPos: vec3 for the camera position in world space camRad: vec3 for camera rotation in radians pmat: typical perspective projection matrix The algorithm / pseudocode: // 1: rayPos is for now "this pixel, as a vector on the view plane in 3d, at The Origin" rayPos.X, rayPos.Y, rayPos.Z = ((fx / width) - 0.5), ((fy / height) - 0.5), 0 // 2: rotate around Y axis depending on cam rotation. No prob since view plane still at Origin 0,0,0 rayPos.MultMat(num.NewDmat4RotationY(camRad.Y)) // 3: a temp vec3. planeDist is -0.15 or some such -- fov-based dist of view plane from eye and also the non-normalized, "in axis-aligned world" traversal step size "forward into the screen" rayStep.X, rayStep.Y, rayStep.Z = 0, 0, planeDist // 4: rotate this too -- 0,zstep should become some meaningful xzstep,xzstep rayStep.MultMat(num.NewDmat4RotationY(CamRad.Y)) // set up direction vector from still-origin-based-ray-position-off-rotated-view-plane plus rotated-zstep-vector rayDir.X, rayDir.Y, rayDir.Z = -rayPos.X - me.rayStep.X, -rayPos.Y, rayPos.Z + rayStep.Z // perspective projection rayDir.Normalize() rayDir.MultMat(pmat) // before traversal, the ray starting position has to be transformed from origin-relative to campos-relative rayPos.Add(camPos) I'm skipping the traversal and sampling parts -- as per screens #1 through #3, those are "basically mostly correct" (though not pretty) -- when axis-aligned / unrotated.

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