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• Cannot get a connection, pool error Timeout waiting for idle object :sakai

  - by siddhant

  iam using sakai 2.9.1 after a few operations the server stops responding and prints log:- 2014-02-20 12:48:47,085 WARN http-bio-8080-exec-18 org.sakaiproject.db.impl.BasicSqlService - Sql.dbRead: sql: select SAKAI_SITE.SITE_ID,SAKAI_SITE.TITLE,SAKAI_SITE.TYPE,SAKAI_SITE.SHO RT_DESC,SAKAI_SITE.DESCRIPTION,SAKAI_SITE.ICON_URL,SAKAI_SITE.INFO_URL,SAKAI_SITE.SKIN,SAKAI_SITE.PUBLISHED,SAKAI_SITE.JOINABLE,SAKAI_SITE.PUBVIEW,SAKAI_SITE.JOIN_ROLE,SAKAI_SITE.IS_SPE CIAL,SAKAI_SITE.IS_USER,SAKAI_SITE.CREATEDBY,SAKAI_SITE.MODIFIEDBY,SAKAI_SITE.CREATEDON,SAKAI_SITE.MODIFIEDON,SAKAI_SITE.CUSTOM_PAGE_ORDERED,SAKAI_SITE.IS_SOFTLY_DELETED,SAKAI_SITE.SOFT LY_DELETED_DATE from SAKAI_SITE where ( SITE_ID = ? ) !admin org.apache.commons.dbcp.SQLNestedException: Cannot get a connection, pool error Timeout waiting for idle object at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:104) at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880) at org.sakaiproject.db.impl.BasicSqlService.borrowConnection(BasicSqlService.java:260) at org.sakaiproject.db.impl.BasicSqlService.dbRead(BasicSqlService.java:540) at org.sakaiproject.util.BaseDbFlatStorage.getResource(BaseDbFlatStorage.java:341) at org.sakaiproject.util.BaseDbFlatStorage.getResource(BaseDbFlatStorage.java:321) at org.sakaiproject.site.impl.DbSiteService$DbStorage.get(DbSiteService.java:236) at org.sakaiproject.site.impl.BaseSiteService.getDefinedSite(BaseSiteService.java:616) at org.sakaiproject.site.impl.BaseSiteService.getSite(BaseSiteService.java:702) at org.sakaiproject.site.impl.BaseSiteService.getSiteVisit(BaseSiteService.java:780) at org.sakaiproject.site.cover.SiteService.getSiteVisit(SiteService.java:140) at org.sakaiproject.presence.tool.PresenceTool.doGet(PresenceTool.java:141) at javax.servlet.http.HttpServlet.service(HttpServlet.java:621) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.sakaiproject.util.RequestFilter.doFilter(RequestFilter.java:634) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:369) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329) at org.sakaiproject.tool.impl.ActiveToolComponent$MyActiveTool.forward(ActiveToolComponent.java:511) at org.sakaiproject.portal.charon.SkinnableCharonPortal.forwardTool(SkinnableCharonPortal.java:1470) at org.sakaiproject.portal.charon.handlers.PresenceHandler.doPresence(PresenceHandler.java:140) at org.sakaiproject.portal.charon.handlers.PresenceHandler.doGet(PresenceHandler.java:70) at org.sakaiproject.portal.charon.SkinnableCharonPortal.doGet(SkinnableCharonPortal.java:881) at javax.servlet.http.HttpServlet.service(HttpServlet.java:621) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.sakaiproject.util.RequestFilter.doFilter(RequestFilter.java:695) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) Caused by: java.util.NoSuchElementException: Timeout waiting for idle object at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1167) at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:96)

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• Revisiting .NET, but what should I focus on?

  - by Wayne M

  After about a two-year hiatus, I'm brushing up on my .NET skills to find a .NET job (my previous two positions have very little development, or development using legacy technologies, so apart from a few very minor apps I have not touched .NET in close to two years). I'm aware of things like ASP.NET MVC, and I have previously read on things like NHibernate and DI/IOC, albeit I have yet to use them apart from very trivial "Hello World" type applications. I have a subscription to Rob Conery's Tekpub website and occasionally watch these videos when I have free time. My concern is this: I don't live in a very technical area. I would be surprised if any but the most tech-savvy companies have heard of, let alone use, ASP.NET MVC, NHibernate (or even LINQ/EF), or know about IoC. I would be willing to bet a large sum of money that 95% of the possible jobs I could obtain will use the following: Visual Source Safe, if any VCS at all ASP.NET 2.0 Webforms (3.5 if lucky) Raw ADO.NET on top of a very thin implementation of the Gateway pattern Stored Procedures in the database for most CRUD operations Gratuitous use of code-behind, with a Service layer if I'm lucky If I were extremely lucky, I might find a shop that has heard of ORMs and either uses one, or has wrote their own data abstraction. Also if I were lucky, the company would be using Model-View-Presenter. In light of this I'm not sure what I should focus on learning. Personally, I would prefer to be using the latest stuff - ASP.NET MVC, NHibernate, jQuery, WCF etc. Reality says I should go back to the basics, since it looks like most potential opportunities aren't going to be anywhere near the cutting edge, or anywhere close to it. And, as much as I would like to find a position and start to show the other developers the benefits, in my past experience this has usually resulted in my being fired for "not being a team player" and doing things the bad old way. So, I am curious how you would approach a situation like this? What should I focus on, in order to A) Reaquaint myself with .NET, and B) Prepare myself to obtain a .NET job again that is more than likely going to use techniques that I and most other knowledgeable developers will scoff at?

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• channel factory null on debug?

  - by Garrith

  When I try to invoke a GetData contract using wcf rest in wcf test client mode I get this message: The Address property on ChannelFactory.Endpoint was null. The ChannelFactory's Endpoint must have a valid Address specified. at System.ServiceModel.ChannelFactory.CreateEndpointAddress(ServiceEndpoint endpoint) at System.ServiceModel.ChannelFactory`1.CreateChannel() at System.ServiceModel.ClientBase`1.CreateChannel() at System.ServiceModel.ClientBase`1.CreateChannelInternal() at System.ServiceModel.ClientBase`1.get_Channel() at Service1Client.GetData(String value) This is the config file for the host: <system.serviceModel> <services> <service name="WcfService1.Service1" behaviorConfiguration="WcfService1.Service1Behavior"> <!-- Service Endpoints --> <endpoint address="http://localhost:26535/Service1.svc" binding="webHttpBinding" contract="WcfService1.IService1" behaviorConfiguration="webHttp" > <!-- Upon deployment, the following identity element should be removed or replaced to reflect the identity under which the deployed service runs. If removed, WCF will infer an appropriate identity automatically. --> <identity> <dns value="localhost"/> </identity> </endpoint> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/> </service> </services> <behaviors> <serviceBehaviors> <behavior name="WcfService1.Service1Behavior"> <!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment --> <serviceMetadata httpGetEnabled="true"/> <!-- To receive exception details in faults for debugging purposes, set the value below to true. Set to false before deployment to avoid disclosing exception information --> <serviceDebug includeExceptionDetailInFaults="false"/> </behavior> </serviceBehaviors> <endpointBehaviors> <behavior name="webHttp"> <webHttp/> </behavior> </endpointBehaviors> </behaviors> </system.serviceModel> </configuration> Code: [ServiceContract(Namespace = "")] public interface IService1 { //[WebInvoke(Method = "POST", UriTemplate = "Data?value={value}")] [OperationContract] [WebGet(UriTemplate = "/{value}")] string GetData(string value); [OperationContract] CompositeType GetDataUsingDataContract(CompositeType composite); // TODO: Add your service operations here } public class Service1 : IService1 { public string GetData(string value) { return string.Format("You entered: {0}", value); }

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• android spinning image

  - by user270811

  hi, i am trying to create two spinning wheels, as in pulleys, so everytime the attached rope moves, the two pulleys will rotate. i have tried two approaches: 1) use Matrix.postRotate within the onDraw() method of the View class, which calls the following: private void drawSpinningWheel(Canvas canvas) { try { canvas.save(); Bitmap bitmapOrg = null; int iDrawable = R.drawable.spinning_button; bitmapOrg = BitmapFactory.decodeResource(getResources(), iDrawable); if(bitmapOrg != null) { int width = bitmapOrg.getWidth(); int height = bitmapOrg.getHeight(); int newWidth = 24; int newHeight = 24; // calculate the scale - in this case = 0.4f float scaleWidth = ((float) newWidth) / width; float scaleHeight = ((float) newHeight) / height; // createa matrix for the manipulation Matrix matrix = new Matrix(); // resize the bit map matrix.postScale(scaleWidth, scaleHeight); matrix.postRotate((float) mDegrees++); Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0, width, height, matrix, true); canvas.drawBitmap(resizedBitmap, matrix, null); } canvas.restore(); } catch(Exception e) { Log.e(TAG + "drawSpinningWheel", e.getMessage()); } } but it seems like the image not only spins but rotates around another axis 2) use SurfaceView and a separate thread, in the run() call this: private void doDraw(Canvas canvas) { // Draw the background image. Operations on the Canvas accumulate // so this is like clearing the screen. canvas.drawBitmap(mBackgroundImage, 0, 0, null); int yTop = mCanvasHeight - ((int) mY + mSpinningWheelImageHeight / 2); int xLeft = (int) mX - mSpinningWheelImageWidth / 2; ... // Draw the ship with its current rotation canvas.save(); canvas.rotate((float) mHeading++, (float) mX, mCanvasHeight - (float) mY); mSpinningWheelImage.setBounds(xLeft, yTop, xLeft + mSpinningWheelImageWidth, yTop + mSpinningWheelImageHeight); mSpinningWheelImage.draw(canvas); canvas.restore(); } i get the spinning to work but i can't add another spinning wheel. i even tried to create another thread for the second spinning wheel, only one shows up. can someone point me in the right direction? thanks.

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• WCF Duplex net.tcp issues on win7

  - by Tom

  We have a WCF service with multiple clients to schedule operations amongst clients. It worked great on XP. Moving to win7, I can only connect a client to the server on the same machine. At this point, I'm thinking it's something to do with IPv6, but I'm stumped as to how to proceed. Client trying to connect to a remote server gives the following exception: System.ServiceModel.EndpointNotFoundException: Could not connect to net.tcp://10.7.11.14:18297/zetec/Service/SchedulerService/Scheduler. The connection attempt lasted for a time span of 00:00:21.0042014. TCP error code 10060: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10.7.11.14:18297. --- System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10.7.11.14:18297 The service is configured like so: <system.serviceModel> <services> <service name="SchedulerService" behaviorConfiguration="SchedulerServiceBehavior"> <host> <baseAddresses> <add baseAddress="net.tcp://localhost/zetec/Service/SchedulerService"/> </baseAddresses> </host> <endpoint address="net.tcp://localhost:18297/zetec/Service/SchedulerService/Scheduler" binding="netTcpBinding" bindingConfiguration = "ConfigBindingNetTcp" contract="IScheduler" /> <endpoint address="net.tcp://localhost:18297/zetec/Service/SchedulerService/Scheduler" binding="netTcpBinding" bindingConfiguration = "ConfigBindingNetTcp" contract="IProcessingNodeControl" /> </service> </services> <bindings> <netTcpBinding> <binding name = "ConfigBindingNetTcp" portSharingEnabled="True"> <security mode="None"/> </binding> </netTcpBinding > </bindings> <behaviors> <serviceBehaviors> <behavior name="SchedulerServiceBehavior"> <serviceDebug includeExceptionDetailInFaults="true" /> <serviceThrottling maxConcurrentSessions="100"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> I've checked my firewall about a dozen times, but I guess there could be something I'm missing. Tried disabling windows firewall. I tried changing localhost to my ipv4 address to try to keep away from ipv6, I've tried removing any anti-ipv6 code.

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• How to serialize parameters in Web Service method

  - by Georgi

  Hi, I have this problem. I have WCF .Net C# web service with this method: public interface IMyService { // TODO: Add your service operations here [OperationContract] ListOfRequests GetListOfRequests(string par1, string par2, string par3, DateTime par4, DateTime par5, string par6, string par7); } public class MyService : IMyService { public ListOfRequests GetListOfRequests(string par1, string par2, string par3, DateTime par4, DateTime par5, string par6, string par7) { // .... web method code here; } } The problem is that when I generate the web service the wsdl schema return this: <xs:element name="GetListOfRequests"> <xs:complexType> <xs:sequence> <xs:element minOccurs="0" name="par1" nillable="true" type="xs:string" /> <xs:element minOccurs="0" name="par2" nillable="true" type="xs:string" /> <xs:element minOccurs="0" name="par3" nillable="true" type="xs:string" /> <xs:element minOccurs="0" name="par4" type="xs:dateTime" /> <xs:element minOccurs="0" name="par5" type="xs:dateTime" /> <xs:element minOccurs="0" name="par6" nillable="true" type="xs:string" /> <xs:element minOccurs="0" name="par7" nillable="true" type="xs:string" /> </xs:sequence> </xs:complexType> </xs:element> and I want my parameters to be not null like this: <xs:element name="GetListOfRequests"> <xs:complexType> <xs:sequence> <xs:element minOccurs="1" name="par1" nillable="false" type="xs:string" /> <xs:element minOccurs="1" name="par2" nillable="false" type="xs:string" /> <xs:element minOccurs="1" name="par3" nillable="false" type="xs:string" /> <xs:element minOccurs="1" name="par4" type="xs:dateTime" /> <xs:element minOccurs="1" name="par5" type="xs:dateTime" /> <xs:element minOccurs="1" name="par6" nillable="false" type="xs:string" /> <xs:element minOccurs="0" name="par7" nillable="true" type="xs:string" /> </xs:sequence> </xs:complexType> </xs:element> How can I serizalize parameters to achieve this? Thank you in advance for your help. Regards, Georgi

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• How to best design a date/geographic proximity query on GAE?

  - by Dane

  Hi all, I'm building a directory for finding athletic tournaments on GAE with web2py and a Flex front end. The user selects a location, a radius, and a maximum date from a set of choices. I have a basic version of this query implemented, but it's inefficient and slow. One way I know I can improve it is by condensing the many individual queries I'm using to assemble the objects into bulk queries. I just learned that was possible. But I'm also thinking about a more extensive redesign that utilizes memcache. The main problem is that I can't query the datastore by location because GAE won't allow multiple numerical comparison statements (<,<=,=,) in one query. I'm already using one for date, and I'd need TWO to check both latitude and longitude, so it's a no go. Currently, my algorithm looks like this: 1.) Query by date and select 2.) Use destination function from geopy's distance module to find the max and min latitude and longitudes for supplied distance 3.) Loop through results and remove all with lat/lng outside max/min 4.) Loop through again and use distance function to check exact distance, because step 2 will include some areas outside the radius. Remove results outside supplied distance (is this 2/3/4 combination inefficent?) 5.) Assemble many-to-many lists and attach to objects (this is where I need to switch to bulk operations) 6.) Return to client Here's my plan for using memcache.. let me know if I'm way out in left field on this as I have no prior experience with memcache or server caching in general. -Keep a list in the cache filled with "geo objects" that represent all my data. These have five properties: latitude, longitude, event_id, event_type (in anticipation of expanding beyond tournaments), and start_date. This list will be sorted by date. -Also keep a dict of pointers in the cache which represent the start and end indices in the cache for all the date ranges my app uses (next week, 2 weeks, month, 3 months, 6 months, year, 2 years). -Have a scheduled task that updates the pointers daily at 12am. -Add new inserts to the cache as well as the datastore; update pointers. Using this design, the algorithm would now look like: 1.) Use pointers to slice off appropriate chunk of list based on supplied date. 2-4.) Same as above algorithm, except with geo objects 5.) Use bulk operation to select full tournaments using remaining geo objects' event_ids 6.) Assemble many-to-manys 7.) Return to client Thoughts on this approach? Many thanks for reading and any advice you can give. -Dane

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• java.lang.Error: "Not enough storage is available to process this command" when generating images

  - by jhericks

  I am running a web application on BEA Weblogic 9.2. Until recently, we were using JDK 1.5.0_04, with JAI 1.1.2_01 and Image IO 1.1. In some circumstances (we never figured out exactly why), when we were processing large images (but not that large - a few MB), the JVM would crash without any error message or stack trace or anything. This didn't happen much in production, but enough to be a nuisance and eventually we were able to reproduce it. We decided to switch to JRockit90 1.5.0_04 and we were no longer able to reproduce the problem in our test environment, so we thought we had it licked. Now, however, after the application server has been up for a while, we start getting the error message, "Not enough storage is available to process this command" during image operations. For example: java.lang.Error: Error starting thread: Not enough storage is available to process this command. at java.lang.Thread.start()V(Unknown Source) at sun.awt.image.ImageFetcher$1.run(ImageFetcher.java:279) at sun.awt.image.ImageFetcher.createFetchers(ImageFetcher.java:272) at sun.awt.image.ImageFetcher.add(ImageFetcher.java:55) at sun.awt.image.InputStreamImageSource.startProduction(InputStreamImageSource.java:149) at sun.awt.image.InputStreamImageSource.addConsumer(InputStreamImageSource.java:106) at sun.awt.image.InputStreamImageSource.startProduction(InputStreamImageSource.java:144) at sun.awt.image.ImageRepresentation.startProduction(ImageRepresentation.java:647) at sun.awt.image.ImageRepresentation.prepare(ImageRepresentation.java:684) at sun.awt.SunToolkit.prepareImage(SunToolkit.java:734) at java.awt.Component.prepareImage(Component.java:3073) at java.awt.ImageMediaEntry.startLoad(MediaTracker.java:906) at java.awt.MediaEntry.getStatus(MediaTracker.java:851) at java.awt.ImageMediaEntry.getStatus(MediaTracker.java:902) at java.awt.MediaTracker.statusAll(MediaTracker.java:454) at java.awt.MediaTracker.waitForAll(MediaTracker.java:405) at java.awt.MediaTracker.waitForAll(MediaTracker.java:375) at SfxNET.System.Drawing.ImageLoader.loadImage(Ljava.awt.Image;)Ljava.awt.image.BufferedImage;(Unknown Source) at SfxNET.System.Drawing.ImageLoader.loadImage(Ljava.net.URL;)Ljava.awt.image.BufferedImage;(Unknown Source) at Resources.Tools.Commands.W$zw(Ljava.lang.ClassLoader;)V(Unknown Source) at Resources.Tools.Commands.getContents()[[Ljava.lang.Object;(Unknown Source) at SfxNET.sfxUtils.SfxResourceBundle.handleGetObject(Ljava.lang.String;)Ljava.lang.Object;(Unknown Source) at java.util.ResourceBundle.getObject(ResourceBundle.java:320) at SoftwareFX.internal.ChartFX.wxvw.yxWW(Ljava.lang.String;Z)Ljava.lang.Object;(Unknown Source) at SoftwareFX.internal.ChartFX.wxvw.vxWW(Ljava.lang.String;)Ljava.lang.Object;(Unknown Source) at SoftwareFX.internal.ChartFX.CommandBar.YWww(LSoftwareFX.internal.ChartFX.wxvw;IIII)V(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.xxvw.YzzW(LSoftwareFX.internal.ChartFX.Internet.Server.ChartCore;Z)LSoftwareFX.internal.ChartFX.CommandBar;(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.xxvw.XzzW(LSoftwareFX.internal.ChartFX.Internet.Server.ChartCore;)V(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.ChartCore.OnDeserialization(Ljava.lang.Object;)V(Unknown Source) at SoftwareFX.internal.ChartFX.Internet.Server.ChartCore.Zvvz(LSoftwareFX.internal.ChartFX.Base.wzzy;)V(Unknown Source) Has anyone seen something like this before? Any clue what might be happening?

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• html widget communicating with server

  - by Nikita Rybak

  I'm making html widget for websites. Let's say, it will display current stock indexes. In short, arbitrary website owner takes code snippet from me and includes it on his webpage http://website.com/index.html. When arbitrary user opens http://website.com/index.html, my code sends request to my server (provider.com), which performs necessary operations and returns information to user's browser. When response has arrived, user will see relevant stock value on http://website.com/index.html. In index.html service could be called like this <script type="text/javascript" src="provider.com/service.js"> </script> <div id="target_area"></div> <script type="text/javascript"> service.show("target_area", options); </script> Now, the problem is in the same origin policy: I can't just send ajax request from website.com to provided.com and return html to embed in client's webpage. I see several solutions, which I list below, but none quite satisfy me. I wonder, if you could suggest something, especially if you had some relevant experience. 1) iframe, plain and simple. Disadvantage: must have fixed dimensions + stupid scroll bars appearing in some browsers. Can be fixed with javascript, but all this browser-specific tinkering doesn't sound good to me. 2) JSONP. Problem: can't return whole chunk of html, must return only data. Then, on browser side, I'll have to use javascript to embed data into html snippet placed statically in index.html. Doesn't sound nice, because data format is not very simple and may even change later. 3) Use hidden iframe to do ajax requests. A bit tricky, but sounds like a way to go. Well, that's my thoughts on the subject. Are there any better ways? BTW, I tried to check some existing widgets too, but didn't find much useful information. All domain names used in this text are fictional and any resemblance is purely coincidental :)

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• Subversion vision and roadmap

  - by gbjbaanb

  Recently C Michael Pilato of the core subversion team posted a mail to the subversion dev mailing list suggesting a vision and roadmap for the future of Subversion. Naturally, he wanted as much feedback and response as possible which is why I'm posting this here - to elicit some suggestions and contributions from you, the users of Subversion. Any comments are welcome, and I shall feedback a synopsis with a link to this question to the dev mailing list. Similarly, I've created a post on ServerFault to get feedback from the administator side of things too. So, without further ado: Vision The first thing on his "vision statement" is: Subversion has no future as a DVCS tool. Let's just get that out there. At least two very successful such tools exist already, and to squeeze another horse into that race would be a poor investment of energy and talent. There's no need to suggest distributed features for subversion. If you want a DVCS, there should be no ill-feeling if you migrate to Git, Mercurial or Bazaar. As he says, its pointless trying to make SVN like them when they already exist, especially when there are different usage patterns that SVN should be targetting. The vision for Subversion is: Subversion exists to be universally recognized and adopted as an open-source, centralized version control system characterized by its reliability as a safe haven for valuable data; the simplicity of its model and usage; and its ability to support the needs of a wide variety of users and projects, from individuals to large-scale enterprise operations. Roadmap Several ideas were suggested as being "very nice to have" and are offered as the starting point of a future roadmap. These are: Obliterate Shelve/Checkpoint Repository-dictated Configuration Rename Tracking Improved Merging Improved Tree Conflict Handling Enterprise Authentication Mechanisms Forward History Searching Log Message Templates If anyone has suggestions to add, or comments on these, the subversion community would welcome all of them. Community And lastly, there was a call for more people to become involved with Subversion development. As with most OSS projects it can be daunting to join, but there is now a push for more to be done to help. If you feel like you can contribute, please do so.

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• How to make custom WCF error handler return JSON response with non-OK http code?

  - by John

  I'm implementing a RESTful web service using WCF and the WebHttpBinding. Currently I'm working on the error handling logic, implementing a custom error handler (IErrorHandler); the aim is to have it catch any uncaught exceptions thrown by operations and then return a JSON error object (including say an error code and error message - e.g. { "errorCode": 123, "errorMessage": "bla" }) back to the browser user along with an an HTTP code such as BadRequest, InteralServerError or whatever (anything other than 'OK' really). Here is the code I am using inside the ProvideFault method of my error handler: fault = Message.CreateMessage(version, "", errorObject, new DataContractJsonSerializer(typeof(ErrorMessage))); var wbf = new WebBodyFormatMessageProperty(WebContentFormat.Json); fault.Properties.Add(WebBodyFormatMessageProperty.Name, wbf); var rmp = new HttpResponseMessageProperty(); rmp.StatusCode = System.Net.HttpStatusCode.InternalServerError; rmp.Headers.Add(HttpRequestHeader.ContentType, "application/json"); fault.Properties.Add(HttpResponseMessageProperty.Name, rmp); -- This returns with Content-Type: application/json, however the status code is 'OK' instead of 'InternalServerError'. fault = Message.CreateMessage(version, "", errorObject, new DataContractJsonSerializer(typeof(ErrorMessage))); var wbf = new WebBodyFormatMessageProperty(WebContentFormat.Json); fault.Properties.Add(WebBodyFormatMessageProperty.Name, wbf); var rmp = new HttpResponseMessageProperty(); rmp.StatusCode = System.Net.HttpStatusCode.InternalServerError; //rmp.Headers.Add(HttpRequestHeader.ContentType, "application/json"); fault.Properties.Add(HttpResponseMessageProperty.Name, rmp); -- This returns with the correct status code, however the content-type is now XML. fault = Message.CreateMessage(version, "", errorObject, new DataContractJsonSerializer(typeof(ErrorMessage))); var wbf = new WebBodyFormatMessageProperty(WebContentFormat.Json); fault.Properties.Add(WebBodyFormatMessageProperty.Name, wbf); var response = WebOperationContext.Current.OutgoingResponse; response.ContentType = "application/json"; response.StatusCode = HttpStatusCode.InternalServerError; -- This returns with the correct status code and the correct content-type! The problem is that the http body now has the text 'Failed to load source for: http://localhost:7000/bla..' instead of the actual JSON data.. Any ideas? I'm considering using the last approach and just sticking the JSON in the HTTP StatusMessage header field instead of in the body, but this doesn't seem quite as nice?

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• Asynchronous readback from opengl front buffer using multiple PBO's

  - by KillianDS

  I am developing an application that needs to read back the whole frame from the front buffer of an openGL application. I can hijack the application's opengl library and insert my code on swapbuffers. At the moment I am successfully using a simple but excruciating slow glReadPixels command without PBO's. Now I read about using multiple PBO's to speed things up. While I think I've found enough resources to actually program that (isn't that hard), I have some operational questions left. I would do something like this: create a series (e.g. 3) of PBO's use glReadPixels in my swapBuffers override to read data from front buffer to a PBO (should be fast and non-blocking, right?) Create a seperate thread to call glMapBufferARB, once per PBO after a glReadPixels, because this will block until the pixels are in client memory. Process the data from step 3. Now my main concern is of course in steps 2 and 3. I read about glReadPixels used on PBO's being non-blocking, will this be an issue if I issue new opengl commands after that very fast? Will those opengl commands block? Or will they continue (my guess), and if so, I guess only swapbuffers can be a problem, will this one stall or will glReadPixels from front buffer be many times faster than swapping (about each 15-30ms) or, worst case scenario, will swapbuffers be executed while glReadPixels is still reading data to the PBO? My current guess is this logic will do something like this: copy FRONT_BUFFER - generic place in VRAM, copy VRAM-RAM. But I have no idea which of those 2 is the real bottleneck and more, what the influence on the normal opengl command stream is. Then in step 3. Is it wise to do this asynchronously in a thread separated from normal opengl logic? At the moment I think not, It seems you have to restore buffer operations to normal after doing this and I can't install synchronization objects in the original code to temporarily block those. So I think my best option is to define a certain swapbuffer delay before reading them out, so e.g. calling glReadPixels on PBO i%3 and glMapBufferARB on PBO (i+2)%3 in the same thread, resulting in a delay of 2 frames. Also, when I call glMapBufferARB to use data in client memory, will this be the bottleneck or will glReadPixels (asynchronously) be the bottleneck? And finally, if you have some better ideas to speed up frame readback from GPU in opengl, please tell me, because this is a painful bottleneck in my current system. I hope my question is clear enough, I know the answer will probably also be somewhere on the internet but I mostly came up with results that used PBO's to keep buffers in video memory and do processing there. I really need to read back the front buffer to RAM and I do not find any clear explanations about performance in that case (which I need, I cannot rely on "it's faster", I need to explain why it's faster). Thank you

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• EJB3 Transaction Propogation

  - by Matt S.

  I have a stateless bean something like: @Stateless public class MyStatelessBean implements MyStatelessLocal, MyStatelessRemote { @PersistenceContext(unitName="myPC") private EntityManager mgr; @TransationAttribute(TransactionAttributeType.SUPPORTED) public void processObjects(List<Object> objs) { // this method just processes the data; no need for a transaction for(Object obj : objs) { this.process(obj); } } @TransationAttribute(TransactionAttributeType.REQUIRES_NEW) public void process(Object obj) { // do some work with obj that must be in the scope of a transaction this.mgr.merge(obj); // ... this.mgr.merge(obj); // ... this.mgr.flush(); } } The typically usage then is the client would call processObjects(...), which doesn't actually interact with the entity manager. It does what it needs to do and calls process(...) individually for each object to process. The duration of process(...) is relatively short, but processObjects(...) could take a very long time to run through everything. Therefore I don't want it to maintain an open transaction. I do need the individual process(...) operations to operate within their own transaction. This should be a new transaction for every call. Lastly I'd like to keep the option open for the client to call process(...) directly. I've tried a number of different transaction types: never, not supported, supported (on processObjects) and required, requires new (on process) but I get TransactionRequiredException every time merge() is called. I've been able to make it work by splitting up the methods into two different beans: @Stateless @TransationAttribute(TransactionAttributeType.NOT_SUPPORTED) public class MyStatelessBean1 implements MyStatelessLocal1, MyStatelessRemote1 { @EJB private MyStatelessBean2 myBean2; public void processObjects(List<Object> objs) { // this method just processes the data; no need for a transaction for(Object obj : objs) { this.myBean2.process(obj); } } } @Stateless public class MyStatelessBean2 implements MyStatelessLocal2, MyStatelessRemote2 { @PersistenceContext(unitName="myPC") private EntityManager mgr; @TransationAttribute(TransactionAttributeType.REQUIRES_NEW) public void process(Object obj) { // do some work with obj that must be in the scope of a transaction this.mgr.merge(obj); // ... this.mgr.merge(obj); // ... this.mgr.flush(); } } but I'm still curious if it's possible to accomplish this in one class. It looks to me like the transaction manager only operates at the bean level, even when individual methods are given more specific annotations. So if I mark one method in a way to prevent the transaction from starting calling other methods within that same instance will also not create a transaction, no matter how they're marked? I'm using JBoss Application Server 4.2.1.GA, but non-specific answers are welcome / preferred.

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• Overriding LINQ extension methods

  - by Ruben Vermeersch

  Is there a way to override extension methods (provide a better implementation), without explicitly having to cast to them? I'm implementing a data type that is able to handle certain operations more efficiently than the default extension methods, but I'd like to keep the generality of IEnumerable. That way any IEnumerable can be passed, but when my class is passed in, it should be more efficient. As a toy example, consider the following: // Compile: dmcs -out:test.exe test.cs using System; namespace Test { public interface IBoat { void Float (); } public class NiceBoat : IBoat { public void Float () { Console.WriteLine ("NiceBoat floating!"); } } public class NicerBoat : IBoat { public void Float () { Console.WriteLine ("NicerBoat floating!"); } public void BlowHorn () { Console.WriteLine ("NicerBoat: TOOOOOT!"); } } public static class BoatExtensions { public static void BlowHorn (this IBoat boat) { Console.WriteLine ("Patched on horn for {0}: TWEET", boat.GetType().Name); } } public class TestApp { static void Main (string [] args) { IBoat niceboat = new NiceBoat (); IBoat nicerboat = new NicerBoat (); Console.WriteLine ("## Both should float:"); niceboat.Float (); nicerboat.Float (); // Output: // NiceBoat floating! // NicerBoat floating! Console.WriteLine (); Console.WriteLine ("## One has an awesome horn:"); niceboat.BlowHorn (); nicerboat.BlowHorn (); // Output: // Patched on horn for NiceBoat: TWEET // Patched on horn for NicerBoat: TWEET Console.WriteLine (); Console.WriteLine ("## That didn't work, but it does when we cast:"); (niceboat as NiceBoat).BlowHorn (); (nicerboat as NicerBoat).BlowHorn (); // Output: // Patched on horn for NiceBoat: TWEET // NicerBoat: TOOOOOT! Console.WriteLine (); Console.WriteLine ("## Problem is: I don't always know the type of the objects."); Console.WriteLine ("## How can I make it use the class objects when the are"); Console.WriteLine ("## implemented and extension methods when they are not,"); Console.WriteLine ("## without having to explicitely cast?"); } } } Is there a way to get the behavior from the second case, without explict casting? Can this problem be avoided?

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• Ajax call to WCF service returns 12031 ERROR_INTERNET_CONNECTION_RESET on new endpoint

  - by cyrix86

  I have extended a WCF service with new functionality in the form of a second service contract. The service.cs now implements both contracts. I have added another endpoint to expose the new contract operations. Here is my web.config relating to the service <system.serviceModel> <bindings> <basicHttpBinding> <binding name="BasicHttpBinding" /> </basicHttpBinding> <webHttpBinding> <binding name="XmlHttpBinding"/> </webHttpBinding> </bindings> <services> <service name="MyNamespace.MyService" behaviorConfiguration="MyServiceBehavior"> <!-- Service Endpoints --> <endpoint address="xmlHttp1" behaviorConfiguration="XmlHttpBehavior" binding="webHttpBinding" bindingConfiguration="XmlHttpBinding" contract="MyNamespace.IContract1" /> <endpoint address="xmlHttp2" binding="webHttpBinding" behaviorConfiguration="XmlHttpBehavior" bindingConfiguration="XmlHttpBinding" contract="MyNamespace.IContract2" /> <endpoint address="" binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding" contract="MyNamespace.IContract1" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="MyServiceBehavior"> <!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment --> <serviceMetadata httpGetEnabled="true"/> <!-- To receive exception details in faults for debugging purposes, set the value below to true. Set to false before deployment to avoid disclosing exception information --> <serviceDebug includeExceptionDetailInFaults="false"/> </behavior> </serviceBehaviors> <endpointBehaviors> <behavior name="XmlHttpBehavior"> <webHttp/> </behavior> </endpointBehaviors> </behaviors> </system.serviceModel> From Javascript, calling 'http://server/wcfServiceApp/MyService.svc/xmlHttp1/Method1' still works fine. Calling 'http://server/wcfServiceApp/MyService.svc/xmlHttp2/Method2' returns the 12031 error. There must be something simple I'm not doing, any help is appreciated.

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• Using QT to build a WYSIWYG Editor for a Custom Markup Language

  - by Aaron

  I'm new to QT, and am trying to figure out the best means of creating a WYSIWYG editor widget for a custom markup language that displays simple text, images, and links. I need to be able to propagate changes from the WYSIWYG editor to the custom markup representation. As a concrete example of the problem domain, imagine that the custom markup might have a "player" tag which contains a player name and a team name. The markup could look like this: Last week, <player id="1234"><name>Aaron Rodgers</name><team>Packers</team></player> threw a pass. This text would display in the editor as: Last week, Aaron Rodgers of the Packers threw a pass. The player name and the team name would be editable directly within the editor in standard WYSIWYG fashion, so that my users do not have to learn any markup. Also, when the player name is moused-over, a details pop-up will appear about that player, and similarly for the team. With that long introduction, I'm trying to figure out where to start with QT. It seems that the most logical option would be the Rich Text API using a QTextDocument. This approach seems less than ideal given the limitations of a QTextDocument: I can't figure out how to capture navigation events from clicking on links. Following links on click seems to only be enabled when the QTextEdit is readonly. Custom objects that implement QTextObjectInterface are ignored in copy-and-paste operations Any HTML-based markup that is passed to it as Rich Text is retranslated into a series of span tags and lots of other junk, making it extremely difficult to propagate changes from the editor back to the original custom markup. A second option appears to be QWebKit, which allows for live editing of HTML5 markup, so I could specify a two-way translation between the custom markup and HTML5. I'm not clear on how one would propagate changes from the editor back to the original markup in real-time without re-translating the entire document on every text change. The QWebKit solutions looks like awfully bulky to me (Learning WebKit along with QT) to what should be a relatively simple problem. I have also considered implementing the WYSIWYG with a custom class using native QT containers, labels, images, and other widgets manually. This seems like the most flexible approach, and the one most likely not to run into unresolvable problems. However, I'm pretty sure that implementing all the details of a normal text editor (selecting text, font changes, cut-and-paste support, undo/redo, dragging of objects, cursor placement, etc.) will be incredibly time consuming. So, finally, my question: are there any QT gurus out there with some advice on where to start with this sort of project? BTW, I am using QT because the application is a desktop application that needs platform independence.

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• C# or C++ game: many 16 color images loaded into RAM. Efficient solution?

  - by user560639

  I am in the planning stages of creating a fighting game and am unsure how to handle one issue relating to memory. Background info: - Still debating whether to use C# (XNA) or C++. We do not want to commit to either until we have explored how to solve this problem in both languages. - Using a max of 256MB RAM would be great if possible. - Two characters will be present at a time, and these characters can only change between battles. There is time to load/free memory between battles, but the game needs to run at a constant 60 drawn frames per second during combat. Each frame is 16.67ms - The total number of images per character is in the low hundreds. Each image is roughly 200x400 pixels. Only one image from each character will be displayed at any given moment. Uncompressed, each image takes roughly 300kb from my calculations; upwards of 100MB for a whole character. This is pushing too close to the 256MB limit given that memory will be needed for some other resources as well. Since each image can be made with a total of 16 colors. Theoretically I should be able to use 1/8th the space if I can take advantage of this. I've looked around but haven't found any word of native support for paletted images. (Storing each pixel using fewer bits that each map to a 32-bit RGBa color) I was considering making my own file format with 4 bits per pixel (and some extra palette info), loading all the images of this new format into RAM before battle, and then when drawing any specific image, decompress only that image into a raw image so it can be rendered properly. I don't know if it's realistic to perform so many assignment operations (appx 200x400 for each character = 160k) each frame. It sounds very hacky to me. Does anyone have advice on whether my solution sounds reasonable, and if there is perhaps a better one available? Thanks so much! (I also attempted to use an image with only 1 channel, then use a shader to perform a series of if statements to translate various values into other colors. Unfortunately, there were too many lines of code for the shader. It is also rather hacky and does not scale well.)

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• Minimum permission required to access Site Columns page and edit site columns

  - by ParanoidMike

  We've started to adopt SharePoint 2010, and are starting to manually migrate content from SharePoint 2007 sites to new sites we're rebuilding from scratch in SP2010. One of the things we previously had supported was to delegate responsibility for managing some of our site columns to a member of the team. The team member is not familiar with SharePoint internals, and doesn't want the responsibility of full permissions to the site and all its objects. We're now trying to figure out what the minimum permission is that we need to grant our team member, so they can continue to edit (& propagate) the content of the site columns we've defined. Permissions he currently has (which are obviously insufficient): Site permissions (according to _layouts/user.aspx): Read, Contribute, Manage Lists Permissions for specific objects in the site (according to _layouts/people.aspxMembershipGroupId=xxx, then choosing Settings, View Group Permissions): server/sites/[sitename]: Contribute server/sites/[sitename]/Lists/[a list with columns that inherit from site columns]: "Contribute No Delete" Note: the "Contribute No Delete" permission is a custom permission I designed by copying the SharePoint-native "Contribute" permission set and deselecting the Delete permission. The "Manage Lists" permission is a custom permission I designed that includes the following specific permissions: (List Permissions) Manage Lists, View Items; (Site Permissions) View Pages, Open. Operations that are throwing access denied errors: _layouts/mngfield.aspx: SharePoint returns the "Error: Access Denied" dialog, and provides three clickable options: "Sign in as a different user", "Request access", and "Go back to site" _layouts/fldedit.aspx?field=Level%5Fx0020%5F3 [one of the site columns we've defined]: can load the page and type in changes to the textboxes "...but when I press OK (save changes) I get the same message above." When our team member clicks the "Request access" link, the email I receive sends me to a page that recommends that I grant the user membership in the "[sitename] Users" group - of which he's already a member. So while SP2010 tries to request access, it doesn't actually direct me to either (a) a valid group that has the correct permissions or (b) the specific object to which I need to grant our team member access. Also note: on the SP2007 (MOSS) site (where our team member was successful in managing Site Column edits), they had dozens of additional permissions throughout the site that we do not wish to blindly re-allocate in SP2010 until we know they're necessary. Any help anyone can provide would be greatly appreciated.

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• Succinct introduction to C++/CLI for C#/Haskell/F#/JS/C++/... programmer

  - by Henrik

  Hello everybody, I'm trying to write integrations with the operating system and with things like active directory and Ocropus. I know a bunch of programming languages, including those listed in the title. I'm trying to learn exactly how C++/CLI works, but can't find succinct, exact and accurate descriptions online from the searching that I have done. So I ask here. Could you tell me the pitfalls and features of C++/CLI? Assume I know all of C# and start from there. I'm not an expert in C++, so some of my questions' answers might be "just like C++", but could say that I am at C#. I would like to know things like: Converting C++ pointers to CLI pointers, Any differences in passing by value/doubly indirect pointers/CLI pointers from C#/C++ and what is 'recommended'. How do gcnew, __gc, __nogc work with Polymorphism Structs Inner classes Interfaces The "fixed" keyword; does that exist? Compiling DLLs loaded into the kernel with C++/CLI possible? Loaded as device drivers? Invoked by the kernel? What does this mean anyway (i.e. to load something into the kernel exactly; how do I know if it is?)? L"my string" versus "my string"? wchar_t? How many types of chars are there? Are we safe in treating chars as uint32s or what should one treat them as to guarantee language indifference in code? Finalizers (~ClassName() {}) are discouraged in C# because there are no garantuees they will run deterministically, but since in C++ I have to use "delete" or use copy-c'tors as to stack allocate memory, what are the recommendations between C#/C++ interactions? What are the pitfalls when using reflection in C++/CLI? How well does C++/CLI work with the IDisposable pattern and with SafeHandle, SafeHandleZeroOrMinusOneIsInvalid? I've read briefly about asynchronous exceptions when doing DMA-operations, what are these? Are there limitations you impose upon yourself when using C++ with CLI integration rather than just doing plain C++? Attributes in C++ similar to Attributes in C#? Can I use the full meta-programming patterns available in C++ through templates now and still have it compile like ordinary C++? Have you tried writing C++/CLI with boost? What are the optimal ways of interfacing the boost library with C++/CLI; can you give me an example of passing a lambda expression to an iterator/foldr function? What is the preferred way of exception handling? Can C++/CLI catch managed exceptions now? How well does dynamic IL generation work with C++/CLI? Does it run on Mono? Any other things I ought to know about?

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• Succinct introduction to C++/CLI for C#/Haskell/F#/JS/C++/... programmer

  - by Henrik

  Hello everybody, I'm trying to write integrations with the operating system and with things like active directory and Ocropus. I know a bunch of programming languages, including those listed in the title. I'm trying to learn exactly how C++/CLI works, but can't find succinct, exact and accurate descriptions online from the searching that I have done. So I ask here. Could you tell me the pitfalls and features of C++/CLI? Assume I know all of C# and start from there. I'm not an expert in C++, so some of my questions' answers might be "just like C++", but could say that I am at C#. I would like to know things like: Converting C++ pointers to CLI pointers, Any differences in passing by value/doubly indirect pointers/CLI pointers from C#/C++ and what is 'recommended'. How do gcnew, __gc, __nogc work with Polymorphism Structs Inner classes Interfaces The "fixed" keyword; does that exist? Compiling DLLs loaded into the kernel with C++/CLI possible? Loaded as device drivers? Invoked by the kernel? What does this mean anyway (i.e. to load something into the kernel exactly; how do I know if it is?)? L"my string" versus "my string"? wchar_t? How many types of chars are there? Are we safe in treating chars as uint32s or what should one treat them as to guarantee language indifference in code? Finalizers (~ClassName() {}) are discouraged in C# because there are no garantuees they will run deterministically, but since in C++ I have to use "delete" or use copy-c'tors as to stack allocate memory, what are the recommendations between C#/C++ interactions? What are the pitfalls when using reflection in C++/CLI? How well does C++/CLI work with the IDisposable pattern and with SafeHandle, SafeHandleZeroOrMinusOneIsInvalid? I've read briefly about asynchronous exceptions when doing DMA-operations, what are these? Are there limitations you impose upon yourself when using C++ with CLI integration rather than just doing plain C++? Attributes in C++ similar to Attributes in C#? Can I use the full meta-programming patterns available in C++ through templates now and still have it compile like ordinary C++? Have you tried writing C++/CLI with boost? What are the optimal ways of interfacing the boost library with C++/CLI; can you give me an example of passing a lambda expression to an iterator/foldr function? What is the preferred way of exception handling? Can C++/CLI catch managed exceptions now? How well does dynamic IL generation work with C++/CLI? Does it run on Mono? Any other things I ought to know about?

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• trying to divide complex numbers, division by zero

  - by user553619

  I'm trying the program below to divide complex numbers, it works for complex numbers but not when the denominator is real (i.e, the complex part is zero). Division by zero occurs in this line ratio = b->r / b->i ;, when the complex part b->i is zero (in the case of a real denominator). How do I get around this? and why did the programmer do this, instead of the more straightforward rule for complex division The wikipedia rule seems to be better, and no division by zero error would occur here. Did I miss something? Why did the programmer not use the wikipedia formula?? Thanks /*! @file dcomplex.c * \brief Common arithmetic for complex type * * <pre> * -- SuperLU routine (version 2.0) -- * Univ. of California Berkeley, Xerox Palo Alto Research Center, * and Lawrence Berkeley National Lab. * November 15, 1997 * * This file defines common arithmetic operations for complex type. * </pre> */ #include <math.h> #include <stdlib.h> #include <stdio.h> #include "slu_dcomplex.h" /*! \brief Complex Division c = a/b */ void z_div(doublecomplex *c, doublecomplex *a, doublecomplex *b) { double ratio, den; double abr, abi, cr, ci; if( (abr = b->r) < 0.) abr = - abr; if( (abi = b->i) < 0.) abi = - abi; if( abr <= abi ) { if (abi == 0) { fprintf(stderr, "z_div.c: division by zero\n"); exit(-1); } ratio = b->r / b->i ; den = b->i * (1 + ratio*ratio); cr = (a->r*ratio + a->i) / den; ci = (a->i*ratio - a->r) / den; } else { ratio = b->i / b->r ; den = b->r * (1 + ratio*ratio); cr = (a->r + a->i*ratio) / den; ci = (a->i - a->r*ratio) / den; } c->r = cr; c->i = ci; }

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• How to create a Uri instance parsed with GenericUriParserOptions.DontCompressPath

  - by Andrew Arnott

  When the .NET System.Uri class parses strings it performs some normalization on the input, such as lower-casing the scheme and hostname. It also trims trailing periods from each path segment. This latter feature is fatal to OpenID applications because some OpenIDs (like those issued from Yahoo) include base64 encoded path segments which may end with a period. How can I disable this period-trimming behavior of the Uri class? Registering my own scheme using UriParser.Register with a parser initialized with GenericUriParserOptions.DontCompressPath avoids the period trimming, and some other operations that are also undesirable for OpenID. But I cannot register a new parser for existing schemes like HTTP and HTTPS, which I must do for OpenIDs. Another approach I tried was registering my own new scheme, and programming the custom parser to change the scheme back to the standard HTTP(s) schemes as part of parsing: public class MyUriParser : GenericUriParser { private string actualScheme; public MyUriParser(string actualScheme) : base(GenericUriParserOptions.DontCompressPath) { this.actualScheme = actualScheme.ToLowerInvariant(); } protected override string GetComponents(Uri uri, UriComponents components, UriFormat format) { string result = base.GetComponents(uri, components, format); // Substitute our actual desired scheme in the string if it's in there. if ((components & UriComponents.Scheme) != 0) { string registeredScheme = base.GetComponents(uri, UriComponents.Scheme, format); result = this.actualScheme + result.Substring(registeredScheme.Length); } return result; } } class Program { static void Main(string[] args) { UriParser.Register(new MyUriParser("http"), "httpx", 80); UriParser.Register(new MyUriParser("https"), "httpsx", 443); Uri z = new Uri("httpsx://me.yahoo.com/b./c.#adf"); var req = (HttpWebRequest)WebRequest.Create(z); req.GetResponse(); } } This actually almost works. The Uri instance reports https instead of httpsx everywhere -- except the Uri.Scheme property itself. That's a problem when you pass this Uri instance to the HttpWebRequest to send a request to this address. Apparently it checks the Scheme property and doesn't recognize it as 'https' because it just sends plaintext to the 443 port instead of SSL. I'm happy for any solution that: Preserves trailing periods in path segments in Uri.Path Includes these periods in outgoing HTTP requests. Ideally works with under ASP.NET medium trust (but not absolutely necessary).

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• System architecture: simple approach for setting up background tasks behind a web application -- wil

  - by Tim Molendijk

  I have a Django web application and I have some tasks that should operate (or actually: be initiated) on the background. The application is deployed as follows: apache2-mpm-worker; mod_wsgi in daemon mode (1 process, 15 threads). The background tasks have the following characteristics: they need to operate in a regular interval (every 5 minutes or so); they require the application context (i.e. the application packages need to be available in memory); they do not need any input other than database access, in order to perform some not-so-heavy tasks such as sending out e-mail and updating the state of the database. Now I was thinking that the most simple approach to this problem would be simply to piggyback on the existing application process (as spawned by mod_wsgi). By implementing the task as part of the application and providing an HTTP interface for it, I would prevent the overhead of another process that is holding all of the application into memory. A simple cronjob can be setup that sends a request to this HTTP interface every 5 minutes and that would be it. Since the application process provides 15 threads and the tasks are quite lightweight and only running every 5 minutes, I figure they would not be hindering the performance of the web application's user-facing operations. Yet... I have done some online research and I have seen nobody advocating this approach. Many articles suggest a significantly more complex approach based on a full-blown messaging component (such as Celery, which uses RabbitMQ). Although that's sexy, it sounds like overkill to me. Some articles suggest setting up a cronjob that executes a script which performs the tasks. But that doesn't feel very attractive either, as it results in creating a new process that loads the entire application into memory, performs some tiny task, and destroys the process again. And this is repeated every 5 minutes. Does not sound like an elegant solution. So, I'm looking for some feedback on my suggested approach as described in the paragraph before the preceeding paragraph. Is my reasoning correct? Am I overlooking (potential) problems? What about my assumption that application's performance will not be impeded?

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• Faster Matrix Multiplication in C#

  - by Kyle Lahnakoski

  I have as small c# project that involves matrices. I am processing large amounts of data by splitting it into n-length chunks, treating the chucks as vectors, and multiplying by a Vandermonde** matrix. The problem is, depending on the conditions, the size of the chucks and corresponding Vandermonde** matrix can vary. I have a general solution which is easy to read, but way too slow: public byte[] addBlockRedundancy(byte[] data) { if (data.Length!=numGood) D.error("Expecting data to be just "+numGood+" bytes long"); aMatrix d=aMatrix.newColumnMatrix(this.mod, data); var r=vandermonde.multiplyBy(d); return r.ToByteArray(); }//method This can process about 1/4 megabytes per second on my i5 U470 @ 1.33GHz. I can make this faster by manually inlining the matrix multiplication: int o=0; int d=0; for (d=0; d<data.Length-numGood; d+=numGood) { for (int r=0; r<numGood+numRedundant; r++) { Byte value=0; for (int c=0; c<numGood; c++) { value=mod.Add(value, mod.Multiply(vandermonde.get(r, c), data[d+c])); }//for output[r][o]=value; }//for o++; }//for This can process about 1 meg a second. (Please note the "mod" is performing operations over GF(2^8) modulo my favorite irreducible polynomial.) I know this can get a lot faster: After all, the Vandermonde** matrix is mostly zeros. I should be able to make a routine, or find a routine, that can take my matrix and return a optimized method which will effectively multiply vectors by the given matrix, but faster. Then, when I give this routine a 5x5 Vandermonde matrix (the identity matrix), there is simply no arithmetic to perform, and the original data is just copied. ** Please note: What I use the term "Vandermonde", I actually mean an Identity matrix with some number of rows from the Vandermonde matrix appended (see comments). This matrix is wonderful because of all the zeros, and because if you remove enough rows (of your choosing) to make it square, it is an invertible matrix. And, of course, I would like to use this same routine to convert any one of those inverted matrices into an optimized series of instructions. How can I make this matrix multiplication faster? Thanks! (edited to correct my mistake with Vandermonde matrix)

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• How to maximize http.sys file upload performance

  - by anelson

  I'm building a tool that transfers very large streaming data sets (possibly on the order of terabytes in a single stream; routinely in the tens of gigabytes) from one server to another. The client portion of the tool will read blocks from the source disk, and send them over the network. The server side will read these blocks off the network and write them to a file on the server disk. Right now I'm trying to decide which transport to use. Options are raw TCP, and HTTP. I really, REALLY want to be able to use HTTP. The HttpListener (or WCF if I want to go that route) make it easy to plug in to the HTTP Server API (http.sys), and I can get things like authentication and SSL for free. The problem right now is performance. I wrote a simple test harness that sends 128K blocks of NULL bytes using the BeginWrite/EndWrite async I/O idiom, with async BeginRead/EndRead on the server side. I've modified this test harness so I can do this with either HTTP PUT operations via HttpWebRequest/HttpListener, or plain old socket writes using TcpClient/TcpListener. To rule out issues with network cards or network pathways, both the client and server are on one machine and communicate over localhost. On my 12-core Windows 2008 R2 test server, the TCP version of this test harness can push bytes at 450MB/s, with minimal CPU usage. On the same box, the HTTP version of the test harness runs between 130MB/s and 200MB/s depending upon how I tweak it. In both cases CPU usage is low, and the vast majority of what CPU usage there is is kernel time, so I'm pretty sure my usage of C# and the .NET runtime is not the bottleneck. The box has two 6-core Xeon X5650 processors, 24GB of single-ranked DDR3 RAM, and is used exclusively by me for my own performance testing. I already know about HTTP client tweaks like ServicePointManager.MaxServicePointIdleTime, ServicePointManager.DefaultConnectionLimit, ServicePointManager.Expect100Continue, and HttpWebRequest.AllowWriteStreamBuffering. Does anyone have any ideas for how I can get HTTP.sys performance beyond 200MB/s? Has anyone seen it perform this well on any environment?

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