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  • Why is my Map broken?

    - by Kirk
    Scenario: Creating a server which has Room objects which contain User objects. I want to store the rooms in a Map of some sort by Id (a string). Desired Behavior: When a user makes a request via the server, I should be able to look up the Room by id from the library and then add the user to the room, if that's what the request needs. Currently I use the static function in my Library.java class where the Map is stored to retrieve Rooms: public class Library { private static Hashtable<String, Rooms> myRooms = new Hashtable<String, Rooms>(); public static addRoom(String s, Room r) { myRooms.put(s, r); } public static Room getRoomById(String s) { return myRooms.get(s); } } In another class I'll do the equivalent of myRoom.addUser(user); What I'm observing using Hashtable, is that no matter how many times I add a user to the Room returned by getRoomById, the user is not in the room later. I thought that in Java, the object that was returned was essentially a reference to the data, the same object that was in the Hashtable with the same references; but, it isn't behaving like that. Is there a way to get this behavior? Maybe with a wrapper of some sort? Am I just using the wrong variant of map? Help?

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  • xmlEncoder not writing in netBeans

    - by Greg
    Hi, I am trying to use the xmlEncoder to write to xml file in net-beans but it doesnt work. Here is the call to the writing function: dbManipulator.writeStudents(deps); where deps = new Hashtable<String, Department>(); dbManipulator = new DataBaseManipulator(); Department is an class-object I made, and here is writeStudents method which is located in the DataBaseManipulator class: public void writeStudents(Hashtable<Integer, Student> students) { XMLEncoder encoder = null; try { encoder = new XMLEncoder(new FileOutputStream(".\\test\\Students.xml")); } catch(Exception e){} encoder.writeObject(students); encoder.close(); }//end of function writeStudents() Any ideas why it isnt working? I tried changing the hashtable to vector but still the xml file looks like that after the writing: <?xml version="1.0" encoding="UTF-8"?> <java version="1.6.0_18" class="java.beans.XMLDecoder"> <object class="java.util.Hashtable"/> </java> Thanks in advance, Greg

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  • How does a hash table work?

    - by Arec Barrwin
    I'm looking for an explanation of how a hashtable works - in plain English for a simpleton like me! For example I know it takes the key, calculates the hash (how?) and then performs some kind of modulo to work out where it lies in the array that the value is stored, but that's where my knowledge stops. Could anyone clarify the process. Edit: I'm not looking specifically about how hashcodes are calculated, but a general overview of how a hashtable works.

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  • ClickOnce manifest problem

    - by TWith2Sugars
    We are currently deploying a WPF 4 app via click once and there is a scenario when the installation fails. If the user does not have .Net 4.0 Full install and attempts to install our app the framework installs fine but the app fails to install. If we re-run the installation again the app installs fine. Here is a copy of the log: PLATFORM VERSION INFO Windows : 6.1.7600.0 (Win32NT) Common Language Runtime : 2.0.50727.4927 System.Deployment.dll : 2.0.50727.4927 (NetFXspW7.050727-4900) mscorwks.dll : 2.0.50727.4927 (NetFXspW7.050727-4900) dfdll.dll : 2.0.50727.4927 (NetFXspW7.050727-4900) dfshim.dll : 4.0.31106.0 (Main.031106-0000) SOURCES Deployment url : [URL REMOVED] Server : Apache/2.0.54 Application url : [URL REMOVED] Server : Apache/2.0.54 IDENTITIES Deployment Identity : Graphicly.App.application, Version=0.3.2.0, Culture=neutral, PublicKeyToken=c982228345371fbc, processorArchitecture=msil Application Identity : Graphicly.App.exe, Version=0.3.2.0, Culture=neutral, PublicKeyToken=c982228345371fbc, processorArchitecture=msil, type=win32 APPLICATION SUMMARY * Installable application. ERROR SUMMARY Below is a summary of the errors, details of these errors are listed later in the log. * Dependency Graphicly.WCFClient.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.WCFClient.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Microsoft.Surface.Presentation.Design.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Microsoft.Surface.Presentation.Design.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency GalaSoft.MvvmLight.WPF4.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file GalaSoft.MvvmLight.WPF4.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.Infrastructure.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.Infrastructure.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.AutoUpdater.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.AutoUpdater.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency System.Windows.Interactivity.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file System.Windows.Interactivity.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Microsoft.Surface.Presentation.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Microsoft.Surface.Presentation.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.Fonts.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.Fonts.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.Reader.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.Reader.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Microsoft.Surface.Presentation.Generic.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Microsoft.Surface.Presentation.Generic.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.Controls.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.Controls.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.SocialNetwork.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.SocialNetwork.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.Archive.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.Archive.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency Graphicly.App.exe cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file Graphicly.App.exe: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Dependency GalaSoft.MvvmLight.Extras.WPF4.dll cannot be processed for patching. Following failure messages were detected: + Exception occurred loading manifest from file GalaSoft.MvvmLight.Extras.WPF4.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. * Activation of [URL REMOVED] resulted in exception. Following failure messages were detected: + Exception occurred loading manifest from file GalaSoft.MvvmLight.Extras.WPF4.dll: the manifest may not be valid or the file could not be opened. + Cannot load internal manifest from component file. COMPONENT STORE TRANSACTION FAILURE SUMMARY No transaction error was detected. WARNINGS * The file named Microsoft.Windows.Design.Extensibility.dll does not have a hash specified in the manifest. Hash validation will be ignored. * The file named Ionic.Zip.Reduced.dll does not have a hash specified in the manifest. Hash validation will be ignored. * The file named Newtonsoft.Json.dll does not have a hash specified in the manifest. Hash validation will be ignored. * The file named Microsoft.WindowsAzure.StorageClient.dll does not have a hash specified in the manifest. Hash validation will be ignored. * The file named Dimebrain.TweetSharp.dll does not have a hash specified in the manifest. Hash validation will be ignored. * The file named Microsoft.Windows.Design.Interaction.dll does not have a hash specified in the manifest. Hash validation will be ignored. * The file named HtmlAgilityPack.dll does not have a hash specified in the manifest. Hash validation will be ignored. * The file named Facebook.dll does not have a hash specified in the manifest. Hash validation will be ignored. OPERATION PROGRESS STATUS * [20/05/2010 09:17:33] : Activation of [URL REMOVED] has started. * [20/05/2010 09:17:38] : Processing of deployment manifest has successfully completed. * [20/05/2010 09:17:38] : Installation of the application has started. * [20/05/2010 09:17:39] : Processing of application manifest has successfully completed. * [20/05/2010 09:17:40] : Request of trust and detection of platform is complete. ERROR DETAILS Following errors were detected during this operation. * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.WCFClient.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Microsoft.Surface.Presentation.Design.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file GalaSoft.MvvmLight.WPF4.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.Infrastructure.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.AutoUpdater.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file System.Windows.Interactivity.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Microsoft.Surface.Presentation.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.Fonts.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.Reader.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:40] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Microsoft.Surface.Presentation.Generic.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:41] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.Controls.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:41] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.SocialNetwork.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:41] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.Archive.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:41] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file Graphicly.App.exe: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:41] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file GalaSoft.MvvmLight.Extras.WPF4.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.FileDownloader.AddFilesInHashtable(Hashtable hashtable, AssemblyManifest applicationManifest, String applicationFolder) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: * [20/05/2010 09:17:41] System.Deployment.Application.InvalidDeploymentException (ManifestLoad) - Exception occurred loading manifest from file GalaSoft.MvvmLight.Extras.WPF4.dll: the manifest may not be valid or the file could not be opened. - Source: System.Deployment - Stack trace: at System.Deployment.Application.Manifest.AssemblyManifest.ManifestLoadExceptionHelper(Exception exception, String filePath) at System.Deployment.Application.Manifest.AssemblyManifest.LoadFromInternalManifestFile(String filePath) at System.Deployment.Application.DownloadManager.ProcessDownloadedFile(Object sender, DownloadEventArgs e) at System.Deployment.Application.FileDownloader.DownloadModifiedEventHandler.Invoke(Object sender, DownloadEventArgs e) at System.Deployment.Application.FileDownloader.PatchSingleFile(DownloadQueueItem item, Hashtable dependencyTable) at System.Deployment.Application.FileDownloader.PatchFiles(SubscriptionState subState) at System.Deployment.Application.FileDownloader.Download(SubscriptionState subState) at System.Deployment.Application.DownloadManager.DownloadDependencies(SubscriptionState subState, AssemblyManifest deployManifest, AssemblyManifest appManifest, Uri sourceUriBase, String targetDirectory, String group, IDownloadNotification notification, DownloadOptions options) at System.Deployment.Application.ApplicationActivator.DownloadApplication(SubscriptionState subState, ActivationDescription actDesc, Int64 transactionId, TempDirectory& downloadTemp) at System.Deployment.Application.ApplicationActivator.InstallApplication(SubscriptionState& subState, ActivationDescription actDesc) at System.Deployment.Application.ApplicationActivator.PerformDeploymentActivation(Uri activationUri, Boolean isShortcut, String textualSubId, String deploymentProviderUrlFromExtension, BrowserSettings browserSettings, String& errorPageUrl) at System.Deployment.Application.ApplicationActivator.ActivateDeploymentWorker(Object state) --- Inner Exception --- System.Deployment.Application.DeploymentException (InvalidManifest) - Cannot load internal manifest from component file. - Source: - Stack trace: COMPONENT STORE TRANSACTION DETAILS No transaction information is available. I'm baffled. Any ideas what this could be? Cheers Tony

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  • When to use a HashTable

    - by ammed
    In C# I find myself using a List, IList or IEnumerable 99% of the time. Is there a case when t would be better to use a HashTable (or Dictionary in 2.0 and above) over these?

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  • Optimal strategy to make a C++ hash table, thread safe

    - by Ajeet
    (I am interested in design of implementation NOT a readymade construct that will do it all.) Suppose we have a class HashTable (not hash-map implemented as a tree but hash-table) and say there are eight threads. Suppose read to write ratio is about 100:1 or even better 1000:1. Case A) Only one thread is a writer and others including writer can read from HashTable(they may simply iterate over entire hash table) Case B) All threads are identical and all could read/write. Can someone suggest best strategy to make the class thread safe with following consideration 1. Top priority to least lock contention 2. Second priority to least number of locks My understanding so far is thus : One BIG reader-writer lock(semaphore). Specialize the semaphore so that there could be eight instances writer-resource for case B, where each each writer resource locks one row(or range for that matter). (so i guess 1+8 mutexes) Please let me know if I am thinking on the correct line, and how could we improve on this solution.

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  • How to store an inventory using hashtables?

    - by Harm De Weirdt
    Hello everyone. For an assignment in collego we have to make a script in Perl that allows us to manage an inventory for an e-store. (The example given was Amazon) Users can make orders in a fully text-based environment and the inventory must be updated when an order is completed. Every item in the inventory has 3 to 4 attributes: a product code, a title, a price and for some an amount (MP3's for example do not have this attribute) Since this is my first encounter with Perl, i don't really know how to start. My main problem is how i should "implement" the inventory in the program. One of the functions of the program is searching trough the titles. Another is to make an order, where the user should give a product code. My first idea was a hashtable with the productcode as key. But if i wanted to search in the titles that could be a problem because of this: the hashkey would be something like DVD-123, the information belonging to that key could be "The Green Mask 12" (without the ") where the 12 indicates how many of this DVD are currently in stock. So i'd have to find a way to ignore the 12 in the end. Another solution was to use the title as Hashkey, but that would prove cumbersome too I think. Is there a way to make a hashtable with 2 key's, and when I give only one it returns an array with the other values? (Including the other key and the other information) That way I could use another key depending on what info I need from my inventory. We have to read the default inventory from a txt file looking like this: MP3-72|Lady Gaga - Kiss and Run (Fear of Commitment Monster)|0.99 CD-400|Kings of Leon - Only By The Night|14.50|2 MP3-401|Kings of Leon - Closer|0.85 DVD-144|Live Free or Die Hard|14.99|2 SOFT-864|Windows Vista|49.95 Any help would be appreciated very much :) PS: I am sorry for my bad grammar, English isn't my native language.

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  • I have got this error : Failed to create InitialContext using factory specified in hashtable

    - by user85121
    I just want to add a servlet in web.xml, like this : <servlet> <display-name>AxisJMSServlet</display-name> <servlet-name>JMSListener</servlet-name> <servlet-class>com.sinosoft.prpall.web.jms.JMSListenServlet</servlet-class> <load-on-startup>110</load-on-startup> </servlet> Everything is just fine, and when i started my programs, I got this : javax.naming.NoInitialContextException: Failed to create InitialContext using factory specified in hashtable [Root exception is java.lang.NullPointerException] at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:258) at javax.naming.InitialContext.initializeDefaultInitCtx(InitialContext.java:318) at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:348) at javax.naming.InitialContext.internalInit(InitialContext.java:286) at javax.naming.InitialContext.<init>(InitialContext.java:211) at org.apache.axis.components.jms.JNDIVendorAdapter.getConnectionFactory(JNDIVendorAdapter.java:85) at org.apache.axis.components.jms.JNDIVendorAdapter.getQueueConnectionFactory(JNDIVendorAdapter.java:55) at org.apache.axis.transport.jms.JMSConnectorFactory.createConnector(JMSConnectorFactory.java:227) at org.apache.axis.transport.jms.JMSConnectorFactory.createServerConnector(JMSConnectorFactory.java:156) at com.sinosoft.prpall.web.jms.JMSListenServlet.init(JMSListenServlet.java:60) at javax.servlet.GenericServlet.init(GenericServlet.java:241) at weblogic.servlet.internal.StubSecurityHelper$ServletInitAction.run(StubSecurityHelper.java:283) at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321) at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120) at weblogic.servlet.internal.StubSecurityHelper.createServlet(StubSecurityHelper.java:64) at weblogic.servlet.internal.StubLifecycleHelper.createOneInstance(StubLifecycleHelper.java:58) at weblogic.servlet.internal.StubLifecycleHelper.<init>(StubLifecycleHelper.java:48) at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:539) at weblogic.servlet.internal.WebAppServletContext.preloadServlet(WebAppServletContext.java:1981) at weblogic.servlet.internal.WebAppServletContext.loadServletsOnStartup(WebAppServletContext.java:1955) at weblogic.servlet.internal.WebAppServletContext.preloadResources(WebAppServletContext.java:1874) Can anybody tell me what is going on ?

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  • Bash: Correct way to Iterate over Map

    - by Lars Tackmann
    In Bash I can create a map (hashtable) with this common construction hput() { eval "$1""$2"='$3' } hget() { eval echo '${'"$1$2"'#hash}' } and then use it like this: hput capitols France Paris hput capitols Spain Madrid echo "$(hget capitols France)" But how do I best iterate over the entries in the map ?. For instance, in Java I would do: for (Map.Entry<String, String> entry : capitols.entrySet()) { System.out.println("Country " + entry.getKey() + " capital " + entry.getValue()); } is there a common way of accomplishing something similar in Bash ?.

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  • are deleted entries counted in the load factor of a hash table using open addressing

    - by Dr. Monkey
    When calculating the load factor of a hashtable with an open-addressing array implementation I am using: numberOfKeysInArray/sizeOfArray however it occurred to me that since deleted entries must be marked as such (to distinguish them from empty spaces), it might make sense to include these in the number of keys. My thinking is that as far as estimating the average number of probes to find an entry, deleted entries should count towards the load factor, but as far as inserting a new key they should not. Which is the proper calculation: including deleted keys or not?

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  • Using hash tables in racket

    - by user2963128
    Im working on an Ngrams program and im having trouble filling out my hash table. i want to write out a recursive function that will take the words and add them to the hash table. The way its supposed to work is given the data set 1 2 3 4 5 6 7 the first entry in the hash table should have a key of [1 2] and the data should be 3. The second entry should be: [2 3] and its data should be 4 and continuing on until the end of the text file. we are given a predefined function called readword that will simply return 1 word from the text. But im not sure how to make these calls overlap each other. The calls would look something like this if the data was hard coded in. (hash-set! (list "1" "2") 3 (hash-set! (list "2" "3") 4 2 calls that ive tried look like this (hash-set! Ngram-table(list((word1) (word2)) readword in))) (hash-set! Ngram-table(append((cdr data) word1)) readword in) apparently the in after readword is supposed to tell the computer that this is and input instead of an output or something like that. How would I call this to make the data in the key of the hashtable overlap like this? And what would the recursive call look like? edit: also we are not allowed to use assigment statements in this program.

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  • Segmentation. strcmp [C]

    - by FILIaS
    Hello, I have a file with format: [name][number][amount] number is taken as a string. and im using it in a strcmp. Problem is that i get a segmentation fault. I know that on most cases when strcmp signs segmentation fault it means that one of the parameters is null or cant find its "end" ('\0'). I checked with gdb and i cant say if this is the problem.Take a look: > (gdb) bt full > #0 0x08048729 in lookup (hashtable=0x804b008, hashval=27, > number=0x804b740 "6900101001") > list = 0xffffffff > #1 0x080487ac in add (hashtable=0x804b008, > number=0x804b740 "9900101001", name=0x804b730 "Smithpolow", > time=6943) > new_elem = 0xffffffff > hashval = 27 > #2 0x08048b25 in main (argc=1, argv=0xbffff4b4) > number = 0x804b740 "9900101001" > name = 0x804b730 "Smithpolow" > time = 6943 > i = 2 Code: clientsList *lookup_on_Clients(clientsHashTable *hashtable,int hashval,char number[10]) { printf("NUMBER:%s\n",number); clientsList *list=hashtable[hashval].head; for(list; list!=NULL; list=list->next){ if (strcmp(number,list->number)==0) //SEGMENTATION! return list; } return NULL; } int add ( HashTable* hashtable,char number[10],char* name,int time) { List *new_elem; int hashval=hash (hashtable,number); new_elem=hashtable[hashval].head; if(hashtable[hashval].length>0) { if ((lookup (hashtable,hashval,number))!=NULL) {return 0;} } //an den uparxei stoixeio sth lista if (!(new_elem=malloc(sizeof(struct clientsList)))){ return -1;} //insert values for the new elem new_elem->number=strdup(number); new_elem->name=strdup(name); new_elem->time=time; hashtable[hashval].head=new_elem; new_elem->next=NULL; hashtable[hashval].length++; /* rehash existing entries if necessary */ if(hashTableSize(hashtable)>= 2*primes[PrimesIndex]) { hashtable = expand(hashtable); if (hashtable ==NULL){ return 0; } PrimesIndex++; } return 1; } and the main: FILE * File2; if ( ( File2=fopen(" File.txt","r")) !=NULL ) { // File.txt format: [name number time] e.g lountemis 6900254565 700651 int li = 0; char *lin = (char *) malloc(MAX_LINE * sizeof(char)); while(fgets(lin, MAX_LINE, clientFile2) != NULL) { token = my_linetok(lin, " "); if(token != NULL) { char* number ; char* name; int time; int i; for(i = 0; token[i] != NULL; i++) { name=strdup(token[0]); number=strdup(token[1]); time=atoi(token[2]); if (i==2) { int insertDone=0; insertDone =add(my_hash_table,number,name,time); } } free(name); free(number); free(token); } else { printf("Error reading line %s\n", lin); exit(1); } } } else { printf("Error opening file \nEXIT!"); exit(0); }

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  • Constructing a hash table/hash function.

    - by nn
    Hi, I would like to construct a hash table that looks up keys in sequences (strings) of bytes ranging from 1 to 15 bytes. I would like to store an integer value, so I imagine an array for hashing would suffice. I'm having difficulty conceptualizing how to construct a hash function such that given the key would give an index into the array. Any assistance would be much appreiated. The maximum number of entries in the hash is: 4081*15 + 4081*14 + ... 4081 = 4081((15*(16))/2) = 489720. So for example: int table[489720]; int lookup(unsigned char *key) { int index = hash(key); return table[index]; } How can I compute hash(key). I'd preferably like to get a perfect hash function. Thanks.

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  • Moving from Linear Probing to Quadratic Probing (hash collisons)

    - by Nazgulled
    Hi, My current implementation of an Hash Table is using Linear Probing and now I want to move to Quadratic Probing (and later to chaining and maybe double hashing too). I've read a few articles, tutorials, wikipedia, etc... But I still don't know exactly what I should do. Linear Probing, basically, has a step of 1 and that's easy to do. When searching, inserting or removing an element from the Hash Table, I need to calculate an hash and for that I do this: index = hash_function(key) % table_size; Then, while searching, inserting or removing I loop through the table until I find a free bucket, like this: do { if(/* CHECK IF IT'S THE ELEMENT WE WANT */) { // FOUND ELEMENT return; } else { index = (index + 1) % table_size; } while(/* LOOP UNTIL IT'S NECESSARY */); As for Quadratic Probing, I think what I need to do is change how the "index" step size is calculated but that's what I don't understand how I should do it. I've seen various pieces of code, and all of them are somewhat different. Also, I've seen some implementations of Quadratic Probing where the hash function is changed to accommodated that (but not all of them). Is that change really needed or can I avoid modifying the hash function and still use Quadratic Probing? EDIT: After reading everything pointed out by Eli Bendersky below I think I got the general idea. Here's part of the code at http://eternallyconfuzzled.com/tuts/datastructures/jsw_tut_hashtable.aspx: 15 for ( step = 1; table->table[h] != EMPTY; step++ ) { 16 if ( compare ( key, table->table[h] ) == 0 ) 17 return 1; 18 19 /* Move forward by quadratically, wrap if necessary */ 20 h = ( h + ( step * step - step ) / 2 ) % table->size; 21 } There's 2 things I don't get... They say that quadratic probing is usually done using c(i)=i^2. However, in the code above, it's doing something more like c(i)=(i^2-i)/2 I was ready to implement this on my code but I would simply do: index = (index + (index^index)) % table_size; ...and not: index = (index + (index^index - index)/2) % table_size; If anything, I would do: index = (index + (index^index)/2) % table_size; ...cause I've seen other code examples diving by two. Although I don't understand why... 1) Why is it subtracting the step? 2) Why is it diving it by 2?

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  • Why am I getting unexpected output trying to write a hash structure to a file?

    - by Harm De Weirdt
    I have a hash in which I store the products a customer buys (%orders). It uses the product code as key and has a reference to an array with the other info as value. At the end of the program, I have to rewrite the inventory to the updated version (i.e. subtract the quantity of the bought items) This is how I do rewrite the inventory: sub rewriteInventory{ open(FILE,'>inv.txt'); foreach $key(%inventory){ print FILE "$key\|$inventory{$key}[0]\|$inventory{$key}[1]\|$inventory{$key}[2]\n" } close(FILE); } where $inventory{$key}[x] is 0 → Title, 1 → price, 2 → quantity. The problem here is that when I look at inv.txt afterwards, I see things like this: CD-911|Lady Gaga - The Fame|15.99|21 ARRAY(0x145030c)||| BOOK-1453|The Da Vinci Code - Dan Brown|14.75|12 ARRAY(0x145bee4)||| Where do these ARRAY(0x145030c)||| entries come from? Or more important, how do I get rid of them?

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  • Help with hash tables and quadratic probing in Java

    - by user313458
    I really need help with inserting into a hash table. I'm just not totally getting it right now. Could someone explain quadratic and linear probing in layman's terms? public void insert(String key) { int homeLocation = 0; int location = 0; int count = 0; if (find(key).getLocation() == -1) // make sure key is not already in the table { //****** ADD YOUR CODE HERE FOR QUADRATIC PROBING ******** } } This is the code I'm working on. I'm not asking anyone to do it, I just really need help with learning the whole concept Any help would be greatly appreciated.

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  • Does it make sense to resize an Hash Table down? And When?

    - by Nazgulled
    Hi, My Hash Table implementation has a function to resize the table when the load reaches about 70%. My Hash Table is implemented with separate chaining for collisions. Does it make sense that I should resize the hash table down at any point or should I just leave it like it is? Otherwise, if I increase the size (by almost double, actually I follow this: http://planetmath.org/encyclopedia/GoodHashTablePrimes.html) when the load is 70%, should I resize it down when the load gets 30% or below?

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  • Good Hash Function for Strings

    - by Leif Andersen
    I'm trying to think up a good hash function for strings. And I was thinking it might be a good idea to sum up the unicode values for the first five characters in the string (assuming it has five, otherwise stop where it ends). Would that be a good idea, or is it a bad one? I am doing this in Java, but I wouldn't imagine that would make much of a difference.

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  • MAD method compression function

    - by Jacques
    I ran across the question below in an old exam. My answers just feels a bit short and inadequate. Any extra ideas I can look into or reasons I have overlooked would be great. Thanx Consider the MAD method compression function, mapping an object with hash code i to element [(3i + 7)mod9027]mod6000 of the 6000-element bucket array. Explain why this is a poor choice of compression function, and how it could be improved. I basically just say that the function could be improved by changing the value for p (or 9027) to an prime number and choosing an other constant for a (or 3) could also help.

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  • How can I test that my hash function is good in terms of max-load?

    - by philcolbourn
    I have read through various papers on the 'Balls and Bins' problem and it seems that if a hash function is working right (ie. it is effectively a random distribution) then the following should/must be true if I hash n values into a hash table with n slots (or bins): Probability that a bin is empty, for large n is 1/e. Expected number of empty bins is n/e. Probability that a bin has k collisions is <= 1/k!. Probability that a bin has at least k collisions is <= (e/k)**k. These look easy to check. But the max-load test (the maximum number of collisions with high probability) is usually stated vaguely. Most texts state that the maximum number of collisions in any bin is O( ln(n) / ln(ln(n)) ). Some say it is 3*ln(n) / ln(ln(n)). Other papers mix ln and log - usually without defining them, or state that log is log base e and then use ln elsewhere. Is ln the log to base e or 2 and is this max-load formula right and how big should n be to run a test? This lecture seems to cover it best, but I am no mathematician. http://pages.cs.wisc.edu/~shuchi/courses/787-F07/scribe-notes/lecture07.pdf BTW, with high probability seems to mean 1 - 1/n.

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