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  • Using Live Data in Database Development Work

    - by Phil Factor
    Guest Editorial for Simple-Talk Newsletter... in which Phil Factor reacts with some exasperation when coming across a report that a majority of companies were still using financial and personal data for both developing and testing database applications. If you routinely test your development work using real production data that contains personal or financial information, you are probably being irresponsible, and at worst, risking a heavy financial penalty for your company. Surprisingly, over 80% of financial companies still do this. Plenty of data breaches and fraud have happened from the use of real data for testing, and a data breach is a nightmare for any organisation that suffers one. The cost of each data breach averages out at around $7.2 million in the US in notification, escalation, credit monitoring, fines, litigation, legal costs, and lost business due to customer churn, £1.9 million in the UK. 70% of data breaches are done from within the organisation. Real data can be exploited in a number of ways for malicious or criminal purposes. It isn't just the obvious use of items such as name and address, date of birth, social security number, and credit card and bank account numbers: Data can be exploited in many subtle ways, so there are excellent reasons to ensure that a high priority is given to the detection and prevention of any data breaches. You'll never successfully guess all the ways that real data can be exploited maliciously, or the ease with which it can be accessed. It would be silly to argue that developers never need access to a copy of the database containing live data. Developers sometimes need to track a bug that can only be replicated on the data from the live database. However, it has to be done in a very restrictive harness. The law makes no distinction between development and production databases when a data breach occurs, so the data has to be held with all appropriate security measures in place. In Europe, the use of personal data for testing requires the explicit consent of the people whose data is being held. There are federal standards such as GLBA, PCI DSS and HIPAA, and most US States have privacy legislation. The task of ensuring compliance and tight security in such circumstances is an expensive and time-consuming overhead. The developer is likely to suffer investigation if a data breach occurs, even if the company manages to stay in business. Ironically, the use of copies of live data isn't usually the most effective way to develop or test your data. Data is usually time-specific and isn't usually current by the time it is used for testing, Existing data doesn't help much for new functionality, and every time the data is refreshed from production, any test data is likely to be overwritten. Also, it is not always going to test all the 'edge' conditions that are likely to flush out bugs. You still have the task of simulating the dynamics of actual usage of the database, and here you have no alternative to creating 'spoofed' data. Because of the complexities of relational data, It used to be that there was no realistic alternative to developing and testing with live data. However, this is no longer the case. Real data can be obfuscated, or it can be created entirely from scratch. The latter process used to be impractical, now that there are plenty of third-party tools to choose from. The process of obfuscation isn't risk free. The process must access the live data, and the success of the obfuscation process has to be carefully monitored. Database data security isn't an exciting topic to you or I, but to a hacker it can be an all-consuming obsession, especially if there is financial or political gain involved. This is not the sort of adversary one would wish for and it is far better to accept, and work with, security restrictions that exist for using live data in database development work, especially when the tools exist to create large realistic database test data that can be better for several aspects of testing.

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  • WebLogic Server Performance and Tuning: Part II - Thread Management

    - by Gokhan Gungor
    WebLogic Server, like any other java application server, provides resources so that your applications use them to provide services. Unfortunately none of these resources are unlimited and they must be managed carefully. One of these resources is threads which are pooled to provide better throughput and performance along with the fast response time and to avoid deadlocks. Threads are execution points that WebLogic Server delivers its power and execute work. Managing threads is very important because it may affect the overall performance of the entire system. In previous releases of WebLogic Server 9.0 we had multiple execute queues and user defined thread pools. There were different queues for different type of work which had fixed number of execute threads.  Tuning of this thread pools and finding the proper number of threads was time consuming which required many trials. WebLogic Server 9.0 and the following releases use a single thread pool and a single priority-based execute queue. All type of work is executed in this single thread pool. Its size (thread count) is automatically decreased or increased (self-tuned). The new “self-tuning” system simplifies getting the proper number of threads and utilizing them.Work manager allows your applications to run concurrently in multiple threads. Work manager is a mechanism that allows you to manage and utilize threads and create rules/guidelines to follow when assigning requests to threads. We can set a scheduling guideline or priority a request with a work manager and then associate this work manager with one or more applications. At run-time, WebLogic Server uses these guidelines to assign pending work/requests to execution threads. The position of a request in the execute queue is determined by its priority. There is a default work manager that is provided. The default work manager should be sufficient for most applications. However there can be cases you want to change this default configuration. Your application(s) may be providing services that need mixture of fast response time and long running processes like batch updates. However wrong configuration of work managers can lead a performance penalty while expecting improvement.We can define/configure work managers at;•    Domain Level: config.xml•    Application Level: weblogic-application.xml •    Component Level: weblogic-ejb-jar.xml or weblogic.xml(For a specific web application use weblogic.xml)We can use the following predefined rules/constraints to manage the work;•    Fair Share Request Class: Specifies the average thread-use time required to process requests. The default is 50.•    Response Time Request Class: Specifies a response time goal in milliseconds.•    Context Request Class: Assigns request classes to requests based on context information.•    Min Threads Constraint: Limits the number of concurrent threads executing requests.•    Max Threads Constraint: Guarantees the number of threads the server will allocate to requests.•    Capacity Constraint: Causes the server to reject requests only when it has reached its capacity. Let’s create a work manager for our application for a long running work.Go to WebLogic console and select Environment | Work Managers from the domain structure tree. Click New button and select Work manager and click next. Enter the name for the work manager and click next. Then select the managed server instances(s) or clusters from available targets (the one that your long running application is deployed) and finish. Click on MyWorkManager, and open the Configuration tab and check Ignore Stuck Threads and save. This will prevent WebLogic to tread long running processes (that is taking more than a specified time) as stuck and enable to finish the process.

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  • The "CreateRiaClientFilesTask" task failed unexpectedly.

    - by Mohammadreza
    Hi guys. I've VS 2010 and recently installed WCF RIA Services V1.0. For testing I have created a new Silverligh Business project but now every now and then when I rebuild the solution I receive the following error: Does anybody know why I get this? Thanks Error 1 The "CreateRiaClientFilesTask" task failed unexpectedly. System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.ServiceModel.DomainServices.Tools, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified. File name: 'Microsoft.ServiceModel.DomainServices.Tools, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMarkHandle stackMark, Boolean loadTypeFromPartialName, ObjectHandleOnStack type) at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark, Boolean loadTypeFromPartialName) at System.RuntimeType.GetType(String typeName, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark) at System.Type.GetType(String typeName, Boolean throwOnError) at System.Web.Hosting.HostingEnvironment.CreateWellKnownObjectInstance(String assemblyQualifiedName, Boolean failIfExists) at System.Web.Hosting.HostingEnvironment.CreateWellKnownObjectInstance(String assemblyQualifiedName, Boolean failIfExists) at System.Web.Hosting.ApplicationManager.CreateObjectInternal(String appId, Type type, IApplicationHost appHost, Boolean failIfExists, HostingEnvironmentParameters hostingParameters) at System.Web.Hosting.ApplicationManager.CreateObjectInternal(String appId, Type type, IApplicationHost appHost, Boolean failIfExists) at System.Web.Compilation.ClientBuildManager.CreateObject(Type type, Boolean failIfExists) at Microsoft.ServiceModel.DomainServices.Tools.CreateRiaClientFilesTask.CreateSharedTypeService(ClientBuildManager clientBuildManager, IEnumerable`1 serverAssemblies, ILogger logger) at Microsoft.ServiceModel.DomainServices.Tools.CreateRiaClientFilesTask.GenerateClientProxies() at Microsoft.ServiceModel.DomainServices.Tools.CreateRiaClientFilesTask.ExecuteInternal() at Microsoft.ServiceModel.DomainServices.Tools.RiaClientFilesTask.Execute() at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask, Boolean& taskResult) WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. BusinessApplication2

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  • What is a good alternative to the WPF WebBrowser Control?

    - by VoidDweller
    I have an MDI WPF app that I need to add web content to. At first, great it looks like I have 2 options built into the framework the Frame control and the WebBrowser control. Given that this is an MDI app it doesn't take long to discover that neither of these will work. The WPF WebBrowser control wraps up the IE WebBrowser ActiveX Control which uses the Win32 graphics pipeline. The "Airspace" issue pretty much sums this up as "Sorry, the layouts will not play nice together". Yes, I have thought about taking snapshots of the web content rendering these and mapping the mouse and keyboard events back to the browser control, but I can't afford the performance penalty and I really don't have time to write and thoroughly test it. I have looked for third party controls, but so far I have only found Chris Cavanagh's WPF Chromium Web Browser control. Which wraps up Awesomium 1.5. Together these are very cool, they play nice with the WPF layouts. But they do not meet my performance requirements. They are VERY HEAVY on memory consumption and not to friendly with CPU usage either. Not to mention still quite buggy. I'll elaborate if you are interested. So, do any of you know of a stable performant WPF web browser control? Thanks.

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  • Negative ItemCount in SharePoint Document Library

    - by ccomet
    What can be done about negative numbers in library item counts? ItemCount is a read-only property, what are you supposed to do when it is drastically incorrect? Earlier last week, I was doing some testing involving the copying and moving of files and folders from one document library to another. I was transfering the items from our actual document library to a sandbox "Test" library that I used to run all sorts of object model and workflow testing in before migrating to the public lists and libraries. I noticed that with files, things worked correctly, but when I copied a folder that had a file inside it (using SPFolder.CopyTo()), the item count for the test library did not actually update. Since this testing was mostly playing around, I paid it little heed. Today I was back in the test library to test a different workflow (regarding PDF conversion). While I was there, I decided to delete the folder I left last week since I didn't need it anymore. And that's when I saw the item count for the list drop to -1 in the All Site Content View. When I deleted the new PDF I had just uploaded, it then dropped to -2! I even checked with the object model... getting an instance of the library I checked the ItemCount property... lo and behold it was also -2. Is there any process which runs in the background, kinda like the one that cleans up workflow history, which will correct this kind of issue? Or is a programmer expected to keep watch for this kind of situation and come up with calculations to compensate the "count penalty", as it were?

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  • "Could not load file or assembly 'System.Web.Mvc, ...

    - by Zack Peterson
    My new ASP.NET MVC Web Application works on my development workstation, but does not run on my web server... Server Error in '/' Application. Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: Could not load file or assembly 'System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified. Source Error: Line 44: <add assembly="System.Web.Abstractions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> Line 45: <add assembly="System.Web.Routing, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> Line 46: <add assembly="System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> Line 47: <add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> Line 48: <add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> Source File: C:\inetpub\www.example.org\web.config Line: 46 Assembly Load Trace: The following information can be helpful to determine why the assembly 'System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' could not be loaded. WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. Version Information: Microsoft .NET Framework Version:2.0.50727.3053; ASP.NET Version:2.0.50727.3053 Do I need to install the AspNetMVCBeta-setup.msi on the server? Or is there a different installer for servers?

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  • FileNotFoundException when running WiX CustomAction with COMAdmin interop

    - by dabcabc
    I am trying to create a WiX custom action which will allow me to shutdown and clear down a COM+ package as part of an upgrade installation, or create and configure a new COM+ package as part of the initial installation. I previously had this running as a CustomAction within a standard Visual Studio MSI but this only allows the custom action to be executed after the files have been copied - which will fail as the package will still be running. The COMAdmin.dll has been added as a reference to the CustomAction project and is set CopyLocal=true. In the bin folder for the custom action project the Interop.COMAdmin.dll is present. The answer to this question seems to suggest that it should work. I am getting the following exception within the MSI log when trying to install: MSI (s) (C4:04) [10:40:34:205]: Invoking remote custom action. DLL: C:\WINDOWS\Installer\MSI119.tmp, Entrypoint: BeforeInstall SFXCA: Extracting custom action to temporary directory: C:\WINDOWS\Installer\MSI119.tmp-\ SFXCA: Binding to CLR version v2.0.50727 Calling custom action MyCustomAction!MyCustomAction.CustomActions.BeforeInstall Exception thrown by custom action: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.IO.FileNotFoundException: Could not load file or assembly 'Interop.COMAdmin, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified. File name: 'Interop.COMAdmin, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' at MyCustomAction.CustomActions.BeforeInstall(Session session) WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value . --- End of inner exception stack trace --- at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture) at Microsoft.Deployment.WindowsInstaller.CustomActionProxy.InvokeCustomAction(Int32 sessionHandle, String entryPoint, IntPtr remotingDelegatePtr)

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  • NAudio demos not working anymore

    - by Kurru
    I just tried to run the NAudio demos and I'm getting a weird error: System.BadImageFormatException: Could not load file or a ssembly 'NAudio, Version=1.3.8.0, Culture=neutral, PublicKeyToken=null' or one o f its dependencies. An attempt was made to load a program with an incorrect form at. File name: 'NAudio, Version=1.3.8.0, Culture=neutral, PublicKeyToken=null' at NAudioWpfDemo.AudioGraph..ctor() at NAudioWpfDemo.ControlPanelViewModel..ctor(IWaveFormRenderer waveFormRender er, SpectrumAnalyser analyzer) in C:\Users\Admin\Downloads\NAudio-1.3\NAudio-1-3 \Source Code\NAudioWpfDemo\ControlPanelViewModel.cs:line 23 at NAudioWpfDemo.MainWindow..ctor() in C:\Users\Admin\Downloads\NAudio-1.3\NA udio-1-3\Source Code\NAudioWpfDemo\MainWindow.xaml.cs:line 15 WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\M icrosoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure lo gging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fus ion!EnableLog]. Since the last time I used NAudio demos I have changed from 32bit Windows XP to 64bit Windows 7. Would this cause this issue? Its very annoying as I was about to try my hand at audio in C# again

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  • Non-blocking TCP buffer issues.

    - by Poni
    Hi! I think I'm in a problem. I have two TCP apps connected to each other which use winsock I/O completion ports to send/receive data (non-blocking sockets). Everything works just fine until there's a data transfer burst. The sender starts sending incorrect/malformed data. I allocate the buffers I'm sending on the stack, and if I understand correctly, that's a wrong to do, because these buffers should remain as I sent them until I get the "write complete" notification from IOCP. Take this for example: void some_function() { char cBuff[1024]; // filling cBuff with some data WSASend(...); // sending cBuff, non-blocking mode // filling cBuff with other data WSASend(...); // again, sending cBuff // ..... and so forth! } If I understand correctly, each of these WSASend() calls should have its own unique buffer, and that buffer can be reused only when the send completes. Correct? Now, what strategies can I implement in order to maintain a big sack of such buffers, how should I handle them, how can I avoid performance penalty, etc'? And, if I am to use buffers that means I should copy the data to be sent from the source buffer to the temporary one, thus, I'd set SO_SNDBUF on each socket to zero, so the system will not re-copy what I already copied. Are you with me? Please let me know if I wasn't clear.

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  • Moses v1.0 multi language ini file

    - by Milan Kocic
    I was working with mosesserver 0.91 and everything works fine but now there is version 1.0 and nothing is same as before. Here is my situation: I want to have multi language translation from arabic to english and from english to arabic. All data and configuration file I have works with 0.91 version of mosesserver. Here is my config file: ------------------------------------------------- ######################### ### MOSES CONFIG FILE ### ######################### # D - decoding path, R - reordering model, L - language model [translation-systems] ar-en D 0 R 0 L 0 en-ar D 1 R 1 L 1 # input factors [input-factors] 0 # mapping steps [mapping] 0 T 0 1 T 1 # translation tables: table type (hierarchical(0), textual (0), binary (1)), source-factors, target-factors, number of scores, file # OLD FORMAT is still handled for back-compatibility # OLD FORMAT translation tables: source-factors, target-factors, number of scores, file # OLD FORMAT a binary table type (1) is assumed [ttable-file] 1 0 0 5 /mnt/models/ar-en/phrase-table/phrase-table 1 0 0 5 /mnt/models/en-ar/phrase-table/phrase-table # no generation models, no generation-file section # language models: type(srilm/irstlm), factors, order, file [lmodel-file] 1 0 5 /mnt/models/ar-en/language-model/en.qblm.mm 1 0 5 /mnt/models/en-ar/language-model/ar.lm.d1.blm.mm # limit on how many phrase translations e for each phrase f are loaded # 0 = all elements loaded [ttable-limit] 20 # distortion (reordering) files [distortion-file] 0-0 wbe-msd-bidirectional-fe-allff 6 /mnt/models/ar-en/reordering-table/reordering-table.wbe-msd-bidirectional-fe.gz 0-0 wbe-msd-bidirectional-fe-allff 6 /mnt/models/en-ar/reordering-model/reordering-table.wbe-msd-bidirectional-fe.gz # distortion (reordering) weight [weight-d] 0.3 0.3 # lexicalised distortion weights [weight-lr] 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 # language model weights [weight-l] 0.5000 0.5000 # translation model weights [weight-t] 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 # no generation models, no weight-generation section # word penalty [weight-w] -1 -1 [distortion-limit] 12 --------------------------------------------------------- So please can someone help me and rewrite this config file so it can work in version 1.0. And i need some python sample code of translation. I am using xmlrpc in python and earler I sent http request with: import xmlrpclib client = xmlrpclib.ServerProxy('http://localhost:8080') client.translate({'text': 'some text', 'system': 'en-ar'}) but now seems there is no more 'system' parameter and moses use always default settings.

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  • Does anyone know of a good Commercial WPF Web Browser Control?

    - by VoidDweller
    I have an MDI WPF app that I need to add web content too. At first, great it looks like I have 2 options built into the framework the Frame control and the WebBrowser control. Given that this is an MDI app it doesn't take long to discover that neither of these will work. The WebBrowser control wraps up the IE WebBrowser ActiveX Control which uses the Win32 graphics pipeline. The "Airspace" issue pretty much sums this up as "Sorry, the layouts will not play nice together". Yes, I have thought about taking snapshots of the web content rendering these and mapping the mouse and keyboard events back to the browser control, but I can't afford the performance penalty and I really don't have time to write and thoroughly test it. I have looked for third party controls, but so far I have only found Chris Cavanagh's WPF Chromium Web Browser control. Which wraps up Awesomium 1.5. Together these are very cool, they play nice with the WPF layouts. But they do not meet my performance requirements. They are VERY HEAVY on memory consumption and not to friendly with CPU usage either. Not to mention still quite buggy. I'll elaborate if you are interested. So, do any of you know of a stable performant WPF web browser control? Thanks.

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  • Using Excel as front end to Access database (with VBA)

    - by Alex
    I am building a small application for a friend and they'd like to be able to use Excel as the front end. (the UI will basically be userforms in Excel). They have a bunch of data in Excel that they would like to be able to query but I do not want to use excel as a database as I don't think it is fit for that purpose and am considering using Access. [BTW, I know Access has its shortcomings but there is zero budget available and Access already on friend's PC] To summarise, I am considering dumping a bunch of data into Access and then using Excel as a front end to query the database and display results in a userform style environment. Questions: How easy is it to link to Access from Excel using ADO / DAO? Is it quite limited in terms of functionality or can I get creative? Do I pay a performance penalty (vs.using forms in Access as the UI)? Assuming that the database will always be updated using ADO / DAO commands from within Excel VBA, does that mean I can have multiple Excel users using that one single Access database and not run into any concurrency issues etc.? Any other things I should be aware of? I have strong Excel VBA skills and think I can overcome Access VBA quite quickly but never really done Excel / Access link before. I could shoehorn the data into Excel and use as a quasi-database but that just seems more pain than it is worth (and not a robust long term solution) Any advice appreciated. Alex

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  • deepcopy and python - tips to avoid using it?

    - by blackkettle
    Hi, I have a very simple python routine that involves cycling through a list of roughly 20,000 latitude,longitude coordinates and calculating the distance of each point to a reference point. def compute_nearest_points( lat, lon, nPoints=5 ): """Find the nearest N points, given the input coordinates.""" points = session.query(PointIndex).all() oldNearest = [] newNearest = [] for n in xrange(nPoints): oldNearest.append(PointDistance(None,None,None,99999.0,99999.0)) newNearest.append(obj2) #This is almost certainly an inappropriate use of deepcopy # but how SHOULD I be doing this?!?! for point in points: distance = compute_spherical_law_of_cosines( lat, lon, point.avg_lat, point.avg_lon ) k = 0 for p in oldNearest: if distance < p.distance: newNearest[k] = PointDistance( point.point, point.kana, point.english, point.avg_lat, point.avg_lon, distance=distance ) break else: newNearest[k] = deepcopy(oldNearest[k]) k += 1 for j in range(k,nPoints-1): newNearest[j+1] = deepcopy(oldNearest[j]) oldNearest = deepcopy(newNearest) #We're done, now print the result for point in oldNearest: print point.station, point.english, point.distance return I initially wrote this in C, using the exact same approach, and it works fine there, and is basically instantaneous for nPoints<=100. So I decided to port it to python because I wanted to use SqlAlchemy to do some other stuff. I first ported it without the deepcopy statements that now pepper the method, and this caused the results to be 'odd', or partially incorrect, because some of the points were just getting copied as references(I guess? I think?) -- but it was still pretty nearly as fast as the C version. Now with the deepcopy calls added, the routine does it's job correctly, but it has incurred an extreme performance penalty, and now takes several seconds to do the same job. This seems like a pretty common job, but I'm clearly not doing it the pythonic way. How should I be doing this so that I still get the correct results but don't have to include deepcopy everywhere?

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  • Stack usage with MMX intrinsics and Microsoft C++

    - by arik-funke
    I have an inline assembler loop that cumulatively adds elements from an int32 data array with MMX instructions. In particular, it uses the fact that the MMX registers can accommodate 16 int32s to calculate 16 different cumulative sums in parallel. I would now like to convert this piece of code to MMX intrinsics but I am afraid that I will suffer a performance penalty because one cannot explicitly intruct the compiler to use the 8 MMX registers to accomulate 16 independent sums. Can anybody comment on this and maybe propose a solution on how to convert the piece of code below to use intrinsics? == inline assembler (only part within the loop) == paddd mm0, [esi+edx+8*0] ; add first & second pair of int32 elements paddd mm1, [esi+edx+8*1] ; add third & fourth pair of int32 elements ... paddd mm2, [esi+edx+8*2] paddd mm3, [esi+edx+8*3] paddd mm4, [esi+edx+8*4] paddd mm5, [esi+edx+8*5] paddd mm6, [esi+edx+8*6] paddd mm7, [esi+edx+8*7] ; add 15th & 16th pair of int32 elements esi points to the beginning of the data array edx provides the offset in the data array for the current loop iteration the data array is arranged such that the elements for the 16 independent sums are interleaved.

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  • How to calculate this string-dissimilarity function efficiently?

    - by ybungalobill
    Hello, I was looking for a string metric that have the property that moving around large blocks in a string won't affect the distance so much. So "helloworld" is close to "worldhello". Obviously Levenshtein distance and Longest common subsequence don't fulfill this requirement. Using Jaccard distance on the set of n-grams gives good results but has other drawbacks (it's a pseudometric and higher n results in higher penalty for changing single character). [original research] As I thought about it, what I'm looking for is a function f(A,B) such that f(A,B)+1 equals the minimum number of blocks that one have to divide A into (A1 ... An), apply a permutation on the blocks and get B: f("hello", "hello") = 0 f("helloworld", "worldhello") = 1 // hello world -> world hello f("abba", "baba") = 2 // ab b a -> b ab a f("computer", "copmuter") = 3 // co m p uter -> co p m uter This can be extended for A and B that aren't necessarily permutations of each other: any additional character that can't be matched is considered as one additional block. f("computer", "combuter") = 3 // com uter -> com uter, unmatched: p and b. Observing that instead of counting blocks we can count the number of pairs of indices that are taken apart by a permutation, we can write f(A,B) formally as: f(A,B) = min { C(P) | P:|A|?|B|, P is bijective, ?i?dom(P) A[P(i)]=B[P(i)] } C(P) = |A| + |B| - |dom(P)| - |{ i | i,i+1?dom(P) and P(i)+1=P(i+1) }| - 1 The problem is... guess what... ... that I'm not able to calculate this in polynomial time. Can someone suggest a way to do this efficiently? Or perhaps point me to already known metric that exhibits similar properties?

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  • Are document-oriented databases any more suitable than relational ones for persisting objects?

    - by Owen Fraser-Green
    In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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  • SEO, ordering and duplication of content

    - by piquadrat
    I run a specialized news site and am trying to apply a little bit of SEO sauce to it. One of the most important things I hear is to avoid duplication of content. I've covered all the basics but I'm stuck with ordering of content. As an example, the archive of the site is orderable by date, views, and rating. Since we don't have that many news items, an archive page for a particular day has usually only a couple of items, so the following URLs all have the same content, albeit in different ordering: /news/archive/2010/05/16/ /news/archive/2010/05/16/?o=views /news/archive/2010/05/16/?o=rating Do search machines penalize this particular kind of duplication of content? And if yes, what's the best way to avoid said penalty? <link rel="canonical" />? Tell Google & Co. to ingore the o parameter? Marking the ordering links with nofollow? Only allow the indexation of the date-ordered archive sites through robots.txt (not sure if this is even possible)?

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  • Rails: creating a custom data type, to use with generator classes and a bunch of questions related t

    - by Shyam
    Hi, After being productive with Rails for some weeks, I learned some tricks and got some experience with the framework. About 10 days ago, I figured out it is possible to build a custom data type for migrations by adding some code in the Table definition. Also, after learning a bit about floating points (and how evil they are) vs integers, the money gem and other possible solutions, I decided I didn't WANT to use the money gem, but instead try to learn more about programming and finding a solution myself. Some suggestions said that I should be using integers, one for the whole numbers and one for the cents. When playing in script/console, I discovered how easy it is to work with calculations and arrays. But, I am talking to much (and the reason I am, is to give some sufficient background). Right now, while playing with the scaffold generator (yes, I use it, because I like they way I can quickly set up a prototype while I am still researching my objectives), I like to use a DRY method. In my opinion, I should build a custom "object", that can hold two variables (Fixnum), one for the whole, one for the cents. In my big dream, I would be able to do the following: script/generate scaffold Cake name:string description:text cost:mycustom Where mycustom should create two integer columns (one for wholes, one for cents). Right now I could do this by doing: script/generate scaffold Cake name:string description:text cost_w:integer cost_c:integer I had also had an idea that would be creating a "cost model", which would hold two columns of integers and create a cost_id column to my scaffold. But wouldn't that be an extra table that would cause some kind of performance penalty? And wouldn't that be defy the purpose of the Cake model in the first place, because the costs are an attribute of individual Cake entries? The reason why I would want to have such a functionality because I am thinking of having multiple "costs" inside my rails application. Thank you for your feedback, comments and answers! I hope my message got through as understandable, my apologies for incorrect grammar or weird sentences as English is not my native language.

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  • Common "truisms" needing correction the most

    - by Charles Bretana
    In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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  • Calculating and saving space in Postgresql

    - by punkish
    I have a table in Pg like so CREATE TABLE t ( a BIGSERIAL NOT NULL, -- 8 b b SMALLINT, -- 2 b c SMALLINT, -- 2 b d REAL, -- 4 b e REAL, -- 4 b f REAL, -- 4 b g INTEGER, -- 4 b h REAL, -- 4 b i REAL, -- 4 b j SMALLINT, -- 2 b k INTEGER, -- 4 b l INTEGER, -- 4 b m REAL, -- 4 b CONSTRAINT a_pkey PRIMARY KEY (a) ) The above adds up to 50 bytes per row. My experience is that I need another 40% to 50% for system overhead, without even any user-created indexes to the above. So, about 75 bytes per row. I will have many, many rows in the table, potentially upward of 145 billion rows, so the table is going to be pushing 13-14 Terabytes. What tricks, if any, could I use to compact this table? My possible ideas below -- Convert the REAL values to INTEGERs. If they can stored as SMALLINT, that is a saving of 2 bytes per field. Convert the columns b .. m into an array. I don't need to search on those columns, but I do need to be able to return one column's value at a time. So, if I need column g, I could do something like SELECT a, arr[5] FROM t; Would I save space with the array option? Would there be a speed penalty? Any other ideas?

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  • What are CDN Best Practices?

    - by Wild Thing
    Hi, I have recently started using the Rackspace Cloudfiles CDN (Limelight), about which I have some questions: I am using jQuery, jQuery UI and jQuery tools in addition to custom JS code. Also, my site is written in ASP.Net, which means there is some ASP.Net generated JS code. Right now what I have done is that I have combined all of the js (including the jquery code), except the ASP.Net generated JS into one file. I am hosting this on the Rackspace CDN. I am wondering if it would make more sense to just get the jQuery, jQuery UI files from the Google hosted CDN (which I suspect would work very well in serving these files, since they will be in many users' cache already)? This would mean one extra HTTP request, so I'm not sure if it'll help. Right now I have multiple containers for my assets. For example, in Rackspace I have 3 containers: JS, CSS and Images. The URL subdomain for all 3 is different. Will that lead to a performance penalty? Should I just use one container (and thus one domain for the CDN)? Is there a way of having the MS ASP.Net generated JS loaded from MS CDN? Would this have a performance hit as per the above question? Thanks in advance, WT

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  • Handling very large lists of objects without paging?

    - by user246114
    Hi, I have a class which can contain many small elements in a list. Looks like: public class Farm { private ArrayList<Horse> mHorses; } just wondering what will happen if the mHorses array grew to something crazy like 15,000 elements. I'm assuming that trying to write and read this from the datastore would be crazy, because I'd get killed on the serialization process. It's important that I can get the entire array in one shot without paging, and each Horse element may only have two string properties in it, so they are pretty lightweight: public class Horse { private String mId; private String mName; } I don't need these horses indexed at all. Does it sound reasonable to just store the mHorse array as a raw Text field, and force my clients to do the deserialization? Something like: public class Farm { private Text mHorsesSerialized; } then whenever the client receives a Farm instance, it has to take the raw string of horses, and split it in order to reinstantiate the list, something like: // GWT client perhaps Farm farm = rpcCall.getMyFarm(); String horsesSerialized = farm.getHorses(); String[] horseBlocks = horsesSerialized.split(","); for (int i = 0; i < horseBlocks.length; i++) { // .. continue deserializing the individual objects ... } yeah... so hopefully it would be quick to read a Farm instance from the datastore, and the serialization penalty is paid by the client, Thanks

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  • Why doesn't String's hashCode() cache 0?

    - by polygenelubricants
    I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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  • Faster way to convert from a String to generic type T when T is a valuetype?

    - by Kumba
    Does anyone know of a fast way in VB to go from a string to a generic type T constrained to a valuetype (Of T as Structure), when I know that T will always be some number type? This is too slow for my taste: Return DirectCast(Convert.ChangeType(myStr, GetType(T)), T) But it seems to be the only sane method of getting from a String -- T. I've tried using Reflector to see how Convert.ChangeType works, and while I can convert from the String to a given number type via a hacked-up version of that code, I have no idea how to jam that type back into T so it can be returned. I'll add that part of the speed penalty I'm seeing (in a timing loop) is because the return value is getting assigned to a Nullable(Of T) value. If I strongly-type my class for a specific number type (i.e., UInt16), then I can vastly increase the performance, but then the class would need to be duplicated for each numeric type that I use. It'd almost be nice if there was converter to/from T while working on it in a generic method/class. Maybe there is and I'm oblivious to its existence?

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  • Embedded Development Board

    - by ALF3130
    I'm new to the embedded development world and am looking to get my very first board. After some research, I realize that there aren't many choices with FPUs. This is important in my project as I'm going to be doing quite a bit of floating point computations. I found the Mini2440 which seems to run on the ARM920T core. This particular unit is perfect for my needs (decent price, all the right I/O ports, and a touch screen to boot) but it seems that it doesn't have an FPU. I don't know how big of a penalty I'd be paying for FP emulation, so I'm unsure of whether to pull the trigger on this one. That said: Can someone please confirm whether this product (Mini2440) has an FPU or not? My project will do image capture and analysis. Does anyone have any experience with running things like OpenMP on such platforms? Please suggest any other similar boards in the = $200 price range that have an FPU. This world is new to me. Any other advice or things I should be aware of is much appreciated.

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