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  • HTTP Headers: Max-Age vs Expires – Which One To Choose?

    - by Gopinath
    Caching of static content like images, scripts, styles on the client browser reduces load on the webservers and also improves end users browsing experience by loading web pages quickly. We can use HTTP headers Expires or Cache-Control:max-age to cache content on client browser and set expiry time for them. Expire header is HTTP/1.0 standard and Cache-Control:max-age is introduced in HTTP/1.1 specification to solve the issues and limitation with Expire  header. Consider the following headers.   Cache-Control: max-age=24560 Expires: Tue, 15 May 2012 06:17:00 GMT The first header instructs web browsers to cache the content for 24560 seconds relative to the time the content is downloaded and expire it after the time period elapses. The second header instructs web browser to expiry the content after 15th May 2011 06:17. Out of these two options which one to use – max-age or expires? I prefer max-age header for the following reasons As max-age  is a relative value and in most of the cases it makes sense to set relative expiry date rather than an absolute expiry date. Expire  header values are complex to set – time format should be proper, time zones should be appropriate. Even a small mistake in settings these values results in unexpected behaviour. As Expire header values are absolute, we need to  keep changing them at regular intervals. Lets say if we set 2011 June 1 as expiry date to all the image files of this blog, on 2011 June 2 we should modify the expiry date to something like 2012 Jan 1. This add burden of managing the Expire headers. Related: Amazon S3 Tips: Quickly Add/Modify HTTP Headers To All Files Recursively cc image flickr:rogue3w This article titled,HTTP Headers: Max-Age vs Expires – Which One To Choose?, was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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  • Passthrough Objects – Duck Typing++

    - by EltonStoneman
    [Source: http://geekswithblogs.net/EltonStoneman] Can't see a genuine use for this, but I got the idea in my head and wanted to work it through. It's an extension to the idea of duck typing, for scenarios where types have similar behaviour, but implemented in differently-named members. So you may have a set of objects you want to treat as an interface, which don't implement the interface explicitly, and don't have the same member names so they can't be duck-typed into implicitly implementing the interface. In a fictitious example, I want to call Get on whichever ICache implementation is current, and have the call passed through to the relevant method – whether it's called Read, Retrieve or whatever: A sample implementation is up on github here: PassthroughSample. This uses Castle's DynamicProxy behind the scenes in the same way as my duck typing sample, but allows you to configure the passthrough to specify how the inner (implementation) and outer (interface) members are mapped:       var setup = new Passthrough();     var cache = setup.Create("PassthroughSample.Tests.Stubs.AspNetCache, PassthroughSample.Tests")                             .WithPassthrough("Name", "CacheName")                             .WithPassthrough("Get", "Retrieve")                             .WithPassthrough("Set", "Insert")                             .As<ICache>(); - or using some ugly Lambdas to avoid the strings :     Expression<Func<ICache, string, object>> get = (o, s) => o.Get(s);     Expression<Func<Memcached, string, object>> read = (i, s) => i.Read(s);     Expression<Action<ICache, string, object>> set = (o, s, obj) => o.Set(s, obj);     Expression<Action<Memcached, string, object>> insert = (i, s, obj) => i.Put(s, obj);       ICache cache = new Passthrough<ICache, Memcached>()                     .Create()                     .WithPassthrough(o => o.Name, i => i.InstanceName)                     .WithPassthrough(get, read)                     .WithPassthrough(set, insert)                     .As();   - or even in config:   ICache cache = Passthrough.GetConfigured<ICache>(); ...  <passthrough>     <types>       <typename="PassthroughSample.Tests.Stubs.ICache, PassthroughSample.Tests"             passesThroughTo="PassthroughSample.Tests.Stubs.AppFabricCache, PassthroughSample.Tests">         <members>           <membername="Name"passesThroughTo="RegionName"/>           <membername="Get"passesThroughTo="Out"/>           <membername="Set"passesThroughTo="In"/>         </members>       </type>   Possibly useful for injecting stubs for dependencies in tests, when your application code isn't using an IoC container. Possibly it also has an alternative implementation using .NET 4.0 dynamic objects, rather than the dynamic proxy.

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  • Modify Build Failure Work Item in TFS 2010 Build

    - by Jakob Ehn
    The default behaviour in TFS Team Build (all versions) is to create a bug work item when a build fails. This main benefit of this is that you get a work item for something that needs to be done, namely to fix the build!. When the developer responsible for the build failure has fixed the problem, he/she can associated that check-in with the work item that was created from the previous build failure. In TFS 2005/2008 you could modify the information in the created work item by changing some predefined properties in the TFSBuild.proj file:   <!-- WorkItemType The type of the work item created on a build failure. --> <WorkItemType>Bug</WorkItemType> <!-- WorkItemFieldValues Fields and values of the work item created on a build failure. Note: Use reference names for fields if you want the build to be resistant to field name changes. Reference names are language independent while friendly names are changed depending on the installed language. For example, "System.Reason" is the reference name for the "Reason" field. --> <WorkItemFieldValues>System.Reason=Build Failure;System.Description=Start the build using Team Build</WorkItemFieldValues> <!-- WorkItemTitle Title of the work item created on build failure. --> <WorkItemTitle>Build failure in build:</WorkItemTitle> <!-- DescriptionText History comment of the work item created on a build failure. --> <DescriptionText>This work item was created by Team Build on a build failure.</DescriptionText> <!-- BuildLogText Additional comment text for the work item created on a build failure. --> <BuildlogText>The build log file is at:</BuildlogText> <!-- ErrorWarningLogText Additional comment text for the work item created on a build failure. This text will only be added if there were errors or warnings. --> <ErrorWarningLogText>The errors/warnings log file is at:</ErrorWarningLogText>   In TFS 2010, with Windows Workflow, you change this by modifying the properties on the OpenWorkItem activity. The hardest part of this is to actually find where this activity is located in the build process workflow. If you open the build definition in XAML you can just search for OpenWorkItem. If you use the designer you need to click your way down to the Catch section of the Try to Compile the Project sequence: To change the default values of the created work item, select the Created Work Item activity and look at the Properties window: Note the CustomFields property which is a dictionary with key (work item field name) and value. If you add custom fields to your work item you can add a value for it here by adding a new entry in the dictionary.

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  • Sixeyed.Caching available now on NuGet and GitHub!

    - by Elton Stoneman
    Originally posted on: http://geekswithblogs.net/EltonStoneman/archive/2013/10/22/sixeyed.caching-available-now-on-nuget-and-github.aspxThe good guys at Pluralsight have okayed me to publish my caching framework (as seen in Caching in the .NET Stack: Inside-Out) as an open-source library, and it’s out now. You can get it here: Sixeyed.Caching source code on GitHub, and here: Sixeyed.Caching package v1.0.0 on NuGet. If you haven’t seen the course, there’s a preview here on YouTube: In-Process and Out-of-Process Caches, which gives a good flavour. The library is a wrapper around various cache providers, including the .NET MemoryCache, AppFabric cache, and  memcached*. All the wrappers inherit from a base class which gives you a set of common functionality against all the cache implementations: •    inherits OutputCacheProvider, so you can use your chosen cache provider as an ASP.NET output cache; •    serialization and encryption, so you can configure whether you want your cache items serialized (XML, JSON or binary) and encrypted; •    instrumentation, you can optionally use performance counters to monitor cache attempts and hits, at a low level. The framework wraps up different caches into an ICache interface, and it lets you use a provider directly like this: Cache.Memory.Get<RefData>(refDataKey); - or with configuration to use the default cache provider: Cache.Default.Get<RefData>(refDataKey); The library uses Unity’s interception framework to implement AOP caching, which you can use by flagging methods with the [Cache] attribute: [Cache] public RefData GetItem(string refDataKey) - and you can be more specific on the required cache behaviour: [Cache(CacheType=CacheType.Memory, Days=1] public RefData GetItem(string refDataKey) - or really specific: [Cache(CacheType=CacheType.Disk, SerializationFormat=SerializationFormat.Json, Hours=2, Minutes=59)] public RefData GetItem(string refDataKey) Provided you get instances of classes with cacheable methods from the container, the attributed method results will be cached, and repeated calls will be fetched from the cache. You can also set a bunch of cache defaults in application config, like whether to use encryption and instrumentation, and whether the cache system is enabled at all: <sixeyed.caching enabled="true"> <performanceCounters instrumentCacheTotalCounts="true" instrumentCacheTargetCounts="true" categoryNamePrefix ="Sixeyed.Caching.Tests"/> <encryption enabled="true" key="1234567890abcdef1234567890abcdef" iv="1234567890abcdef"/> <!-- key must be 32 characters, IV must be 16 characters--> </sixeyed.caching> For AOP and methods flagged with the cache attribute, you can override the compile-time cache settings at runtime with more config (keyed by the class and method name): <sixeyed.caching enabled="true"> <targets> <target keyPrefix="MethodLevelCachingStub.GetRandomIntCacheConfiguredInternal" enabled="false"/> <target keyPrefix="MethodLevelCachingStub.GetRandomIntCacheExpiresConfiguredInternal" seconds="1"/> </targets> It’s released under the MIT license, so you can use it freely in your own apps and modify as required. I’ll be adding more content to the GitHub wiki, which will be the main source of documentation, but for now there’s an FAQ to get you started. * - in the course the framework library also wraps NCache Express, but there's no public redistributable library that I can find, so it's not in Sixeyed.Caching.

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  • Willy Rotstein on Analytics and Social Media in Retail

    - by sarah.taylor(at)oracle.com
    Recently I came across a presentation from Dan Zarrella on "The Science of Retweets. (http://www.slideshare.net/HubSpot/the-science-of-retweets-with-dan-zarrella). It is an insightful, fact-based analysis of how tweets propagate and what makes them successful. The analysis is of course very interesting for those of us interested Tweeting. However, what really caught my attention is how well it illustrates, form a very different angle, some of the issues I am discussing with retailers these days. In particular the opportunities that e-commerce and social media open to those retailers with the appetite and vision to tackle the associated analytical challenges. And these challenges are of course not straightforward.   In his presentation Dan introduces the concept of Observability, I haven't had the opportunity to discuss with Dan his specific definition for the term. However, in practical retail terms, I would say that it means that through social media (and other web channels such as search) we can analyze and track processes by measuring Indicators that were not measurable before. The focus is in identifying patterns across a large number of consumers rather than what a particular individual "Likes".   The potential impact for retailers is huge. It opens the opportunity to monitor changes in consumer preference  and plan the business accordingly. And you can do this almost "real time" rather than through infrequent surveys that provide a "rear view" picture of your consumer behaviour. For instance, you could envision identifying when a particular set of fashion styles are breaking out from the pack, and commit a re-buy. Or you could monitor when the preference for a specific mobile device has declined and hence markdowns should be considered; or how demand for a specific ready-made food typically flows across regions and manage the inventory accordingly. Search, blogging, website and store data may need to be considered in identifying these trends. The data volumes involved are huge (check Andrea Morgan's recent post on "Big Data" in retail) but so are the benefits. As Andrea says, for the first time we can start getting insight into "Why" the business is performing in a certain way rather than just reporting on what is happening. And it is not just about the data volumes. Tackling the challenge also calls for integrated planning systems that can bring data and insight into the context of the Decision Making process Buyers, Merchandisers and Supply Chain managers are following. I strongly believe that only when data and process come together you can move from the anecdotal to systematically improving business performance.   I would love to hear your opinions on these trends and where you think Retail is heading to exploit these topics - please email me: [email protected]

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  • Subterranean IL: Filter exception handlers

    - by Simon Cooper
    Filter handlers are the second type of exception handler that aren't accessible from C#. Unlike the other handler types, which have defined conditions for when the handlers execute, filter lets you use custom logic to determine whether the handler should be run. However, similar to a catch block, the filter block does not get run if control flow exits the block without throwing an exception. Introducing filter blocks An example of a filter block in IL is the following: .try { // try block } filter { // filter block endfilter }{ // filter handler } or, in v1 syntax, TryStart: // try block TryEnd: FilterStart: // filter block HandlerStart: // filter handler HandlerEnd: .try TryStart to TryEnd filter FilterStart handler HandlerStart to HandlerEnd In the v1 syntax there is no end label specified for the filter block. This is because the filter block must come immediately before the filter handler; the end of the filter block is the start of the filter handler. The filter block indicates to the CLR whether the filter handler should be executed using a boolean value on the stack when the endfilter instruction is run; true/non-zero if it is to be executed, false/zero if it isn't. At the start of the filter block, and the corresponding filter handler, a reference to the exception thrown is pushed onto the stack as a raw object (you have to manually cast to System.Exception). The allowed IL inside a filter block is tightly controlled; you aren't allowed branches outside the block, rethrow instructions, and other exception handling clauses. You can, however, use call and callvirt instructions to call other methods. Filter block logic To demonstrate filter block logic, in this example I'm filtering on whether there's a particular key in the Data dictionary of the thrown exception: .try { // try block } filter { // Filter starts with exception object on stack // C# code: ((Exception)e).Data.Contains("MyExceptionDataKey") // only execute handler if Contains returns true castclass [mscorlib]System.Exception callvirt instance class [mscorlib]System.Collections.IDictionary [mscorlib]System.Exception::get_Data() ldstr "MyExceptionDataKey" callvirt instance bool [mscorlib]System.Collections.IDictionary::Contains(object) endfilter }{ // filter handler // Also starts off with exception object on stack callvirt instance string [mscorlib]System.Object::ToString() call void [mscorlib]System.Console::WriteLine(string) } Conclusion Filter exception handlers are another exception handler type that isn't accessible from C#, however, just like fault handlers, the behaviour can be replicated using a normal catch block: try { // try block } catch (Exception e) { if (!FilterLogic(e)) throw; // handler logic } So, it's not that great a loss, but it's still annoying that this functionality isn't directly accessible. Well, every feature starts off with minus 100 points, so it's understandable why something like this didn't make it into the C# compiler ahead of a different feature.

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  • Certificate Revocation checking affecting system performance [migrated]

    - by Colm Clarke
    I have a .NET 3.5 desktop application that had been showing periodic slow downs in functionality whenever the test machine it was on was out of the office. I managed to replicate the error on a machine in the office without an internet connection, but it was only when i used ANTS performance profiler that i got a clearer picture of what was going on. In ANTS I saw a "Waiting for synchronization" taking up to 16 seconds that corresponded to the delay I could see in the application when NHibernate tried to load the System.Data.SqlServerCE.dll assembly. If I tried the action again immediately it would work with no delay but if I left it for 5 minutes then it would be slow to load again the next time I tried it. From my research so far it appears to be because the SqlServerCE dll is signed and so the system is trying to connect to get the certificate revocation lists and timing out. Disabling the "Automatically detect settings" setting in the Internet Options LAN settings makes the problem go away, as does disabling the "Check for publishers certificate revocation". But the admins where this application will be deployed are not going to be happy with the idea of disabling certificate checking on a per machine or per user basis so I really need to get the application level disabling of the CRL check working. There is the well documented bug in .net 2.0 which describes this behaviour, and offers a possible fix with a config file element. <?xml version="1.0" encoding="utf-8"?> <configuration> <runtime> <generatePublisherEvidence enabled="false"/> </runtime> </configuration> This is NOT working for me however even though I am using .net 3.5. The SQLServerCE dll is being loaded dynamically by NHibernate and I wonder if the fact that it's dynamic could somehow be why the setting isn't working, but I don't know how I could check that. Can anyone offer suggestions as to why the config setting might not work? Or is there another way I could disable the check at the application level, perhaps a CAS policy setting that I can use to set an exception for the application when it's installed? Or is there something I can change in the application to up the trust level or something like that? I have also tried using to no advantage ServicePointManager.CheckCertificateRevocationList = false; http://rusanu.com/2009/07/24/fix-slow-application-startup-due-to-code-sign-validation/ I have also tried those registry settings out and unfortunately they didn't help. The dlls that appear to be the cause of the hold up are native SQL Server CE dlls, and looking at the stack traces in ProcMon mscorwks.dll doesn't appear to be involved even though the checks on crypto and cert registry keys are being done under the .NET application. It's definitely still something to do with publisher certificate checking because unticking "Check for publisher revocation certificate" still works but something odd is going on.

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  • How To Fix YouTube Re-Buffering On Full Screen Issue

    - by Gopinath
    YouTube has an annoying bug – videos starts re-buffering when we switch to full screen mode from normal mode. On a high speed broadband connection the re-buffering issue may not be annoying much but on a slow broadband connection it annoys hell out of us. When users reported this problem to YouTube, the engineers at YouTube dubbed it as a feature rather than bug!. That is sick and this behaviour shows that they started ignoring the users and their problem. Anyways we got solutions to get around this annoying issue. Root Cause Of The Issue The root cause of the bug is YouTube’s resolution switching mechanism.When the video is loaded in normal model it is buffered and played at 360p, but when the full screen mode is activated YouTube player switches to 480p and starts re-buffering the video. How To Fix The Issue on Google Chrome Browser Fixing this issue on Google Chrome is very simple. All we need to do is to install this Greasemonkey script and it fixes everything for you. How To Fix The Issue on Firefox Browser Fixing this issue on Firefox browser involves an extra step when compared to Chrome browser. To fix the issue Step 1: Install Greasemonkey Addon for Firefox Step 2: Install this script from userscripts.org Done. Firefox will handle the full screen switching smoothly. How To Fix The Issue on Internet Explorer Hufff!! Internet Explorer users are poor users not because they are dumb but because they are using stone age browser. No offense, IE is a pathetic browser and there is no support for Greasemonkey scripts. Anyway lets look at the solution for fixing YouTube issue on IE. To fix the YouTube bug you need to follow the official solution provided by Google and it’s not a friendly one. Step 1: Login to your YouTube account and select the option “I have a slow connection. Never play higher-quality video“. Step 2 – Repeat Always: Make sure that you are always logged into your YouTube account as YouTube need to know your settings before switching the resolution. (Now you know why I called IE as a poor browser). Related: Set the start time of a YouTube Video This article titled,How To Fix YouTube Re-Buffering On Full Screen Issue, was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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  • SBUG Session: The Enterprise Cache

    - by EltonStoneman
    [Source: http://geekswithblogs.net/EltonStoneman] I did a session on "The Enterprise Cache" at the UK SOA/BPM User Group yesterday which generated some useful discussion. The proposal was for a dedicated caching layer which all app servers and service providers can hook into, sharing resources and common data. The architecture might end up like this: I'll update this post with a link to the slide deck once it's available. The next session will have Udi Dahan walking through nServiceBus, register on EventBrite if you want to come along. Synopsis Looked at the benefits and drawbacks of app-centric isolated caches, compared to an enterprise-wide shared cache running on dedicated nodes; Suggested issues and risks around caching including staleness of data, resource usage, performance and testing; Walked through a generic service cache implemented as a WCF behaviour – suitable for IIS- or BizTalk-hosted services - which I'll be releasing on CodePlex shortly; Listed common options for cache providers and their offerings. Discussion Cache usage. Different value propositions for utilising the cache: improved performance, isolation from underlying systems (e.g. service output caching can have a TTL large enough to cover downtime), reduced resource impact – CPU, memory, SQL and cost (e.g. caching results of paid-for services). Dedicated cache nodes. Preferred over in-host caching provided latency is acceptable. Depending on cache provider, can offer easy scalability and global replication so cache clients always use local nodes. Restriction of AppFabric Caching to Windows Server 2008 not viewed as a concern. Security. Limited security model in most cache providers. Options for securing cache content suggested as custom implementations. Obfuscating keys and serialized values may mean additional security is not needed. Depending on security requirements and architecture, can ensure cache servers only accessible to cache clients via IPsec. Staleness. Generally thought to be an overrated problem. Thinking in line with eventual consistency, that serving up stale data may not be a significant issue. Good technical arguments support this, although I suspect business users will be harder to persuade. Providers. Positive feedback for AppFabric Caching – speed, configurability and richness of the distributed model making it a good enterprise choice. .NET port of memcached well thought of for performance but lack of replication makes it less suitable for these shared scenarios. Replicated fork – repcached – untried and less active than memcached. NCache also well thought of, but Express version too limited for enterprise scenarios, and commercial versions look costly compared to AppFabric.

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  • Working with EO composition associations via ADF BC SDO web services

    - by Chris Muir
    ADF Business Components support the ability to publish the underlying Application Modules (AMs) and View Objects (VOs) as web services through Service Data Objects (SDOs).  This blog post looks at a minor challenge to overcome when using SDOs and Entity Objects (EOs) that use a composition association. Using the default ADF BC EO association behaviour ADF BC components allow you to work with VOs that are based on EOs that are a part of a parent-child composition association.  A composition association enforces that you cannot create records for the child outside the context of the parent.  As example when creating invoice-lines you want to enforce the individual lines have a relating parent invoice record, it just simply doesn't make sense to save invoice-lines without their parent invoice record. In the following screenshot using the ADF BC Tester it demonstrates the correct way to create a child Employees record as part of a composition association with Departments: And the following screenshot shows you the wrong way to create an Employee record: Note the error which is enforced by the composition association: (oracle.jbo.InvalidOwnerException) JBO-25030: Detail entity Employees with row key null cannot find or invalidate its owning entity.  Working with composition associations via the SDO web services  Shay Shmeltzer recently recorded a good video which demonstrates how to expose your ADF Business Components through the SDO interface. On exposing the VOs you get a choice of operation to publish including create, update, delete and more: For example through the SDO test interface we can see that the create operation will request the attributes for the VO exposed, in this case EmployeesView1: In this specific case though, just like the ADF BC Tester, an attempt to create this record will fail with JBO-25030, the composition association is still enforced: The correct way to to do this is through the create operation on the DepartmentsView1 which also lets you create employees record in context of the parent, thus satisfying the composition association rule: Yet at issue here is the create operation will always create both the parent Departments and Employees records.  What do we do if we've already previously created the parent Departments records, and we just want to create additional Employees records for that Department?  The create method of the EmployeeView1 as we saw previously doesn't allow us to do that, the JBO-3050 error will be raised. The solution is the "merge" operation on the parent Departments record: In this case for the Departments record you just need to supply the DepartmentId of the Department you want the Employees record to be associated with, as well as the new Employees record.  When invoked only the Employees record is created, and the supply of the DepartmentId of the Departments record satisfies the composition association without actually creating or updating the associated Department record that already exists in the database. Be warned however if you supply any more attributes for the Department record, it will result in a merge (update) of the associated Departments record too. 

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  • Brendan Gregg's "Systems Performance: Enterprise and the Cloud"

    - by user12608550
    Long ago, the prerequisite UNIX performance book was Adrian Cockcroft's 1994 classic, Sun Performance and Tuning: Sparc & Solaris, later updated in 1998 as Java and the Internet. As Solaris evolved to include the invaluable DTrace observability features, new essential performance references have been published, such as Solaris Performance and Tools: DTrace and MDB Techniques for Solaris 10 and OpenSolaris (2006)  by McDougal, Mauro, and Gregg, and DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD (2011), also by Mauro and Gregg. Much has occurred in Solaris Land since those books appeared, notably Oracle's acquisition of Sun Microsystems in 2010 and the demise of the OpenSolaris community. But operating system technologies have continued to improve markedly in recent years, driven by stunning advances in multicore processor architecture, virtualization, and the massive scalability requirements of cloud computing. A new performance reference was needed, and I eagerly waited for something that thoroughly covered modern, distributed computing performance issues from the ground up. Well, there's a new classic now, authored yet again by Brendan Gregg, former Solaris kernel engineer at Sun and now Lead Performance Engineer at Joyent. Systems Performance: Enterprise and the Cloud is a modern, very comprehensive guide to general system performance principles and practices, as well as a highly detailed reference for specific UNIX and Linux observability tools used to examine and diagnose operating system behaviour.  It provides thorough definitions of terms, explains performance diagnostic Best Practices and "Worst Practices" (called "anti-methods"), and covers key observability tools including DTrace, SystemTap, and all the traditional UNIX utilities like vmstat, ps, iostat, and many others. The book focuses on operating system performance principles and expands on these with respect to Linux (Ubuntu, Fedora, and CentOS are cited), and to Solaris and its derivatives [1]; it is not directed at any one OS so it is extremely useful as a broad performance reference. The author goes beyond the intricacies of performance analysis and shows how to interpret and visualize statistical information gathered from the observability tools.  It's often difficult to extract understanding from voluminous rows of text output, and techniques are provided to assist with summarizing, visualizing, and interpreting the performance data. Gregg includes myriad useful references from the system performance literature, including a "Who's Who" of contributors to this great body of diagnostic tools and methods. This outstanding book should be required reading for UNIX and Linux system administrators as well as anyone charged with diagnosing OS performance issues.  Moreover, the book can easily serve as a textbook for a graduate level course in operating systems [2]. [1] Solaris 11, of course, and Joyent's SmartOS (developed from OpenSolaris) [2] Gregg has taught system performance seminars for many years; I have also taught such courses...this book would be perfect for the OS component of an advanced CS curriculum.

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  • Subterranean IL: Fault exception handlers

    - by Simon Cooper
    Fault event handlers are one of the two handler types that aren't available in C#. It behaves exactly like a finally, except it is only run if control flow exits the block due to an exception being thrown. As an example, take the following method: .method public static void FaultExample(bool throwException) { .try { ldstr "Entering try block" call void [mscorlib]System.Console::WriteLine(string) ldarg.0 brfalse.s NormalReturn ThrowException: ldstr "Throwing exception" call void [mscorlib]System.Console::WriteLine(string) newobj void [mscorlib]System.Exception::.ctor() throw NormalReturn: ldstr "Leaving try block" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } fault { ldstr "Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } Return: ldstr "Returning from method" call void [mscorlib]System.Console::WriteLine(string) ret } If we pass true to this method the following gets printed: Entering try block Throwing exception Fault handler and the exception gets passed up the call stack. So, the exception gets thrown, the fault handler gets run, and the exception propagates up the stack afterwards in the normal way. If we pass false, we get the following: Entering try block Leaving try block Returning from method Because we are leaving the .try using a leave.s instruction, and not throwing an exception, the fault handler does not get called. Fault handlers and C# So why were these not included in C#? It seems a pretty simple feature; one extra keyword that compiles in exactly the same way, and with the same semantics, as a finally handler. If you think about it, the same behaviour can be replicated using a normal catch block: try { throw new Exception(); } catch { // fault code goes here throw; } The catch block only gets run if an exception is thrown, and the exception gets rethrown and propagates up the call stack afterwards; exactly like a fault block. The only complications that occur is when you want to add a fault handler to a try block with existing catch handlers. Then, you either have to wrap the try in another try: try { try { // ... } catch (DirectoryNotFoundException) { // ... // leave.s as normal... } catch (IOException) { // ... throw; } } catch { // fault logic throw; } or separate out the fault logic into another method and call that from the appropriate handlers: try { // ... } catch (DirectoryNotFoundException ) { // ... } catch (IOException ioe) { // ... HandleFaultLogic(); throw; } catch (Exception e) { HandleFaultLogic(); throw; } To be fair, the number of times that I would have found a fault handler useful is minimal. Still, it's quite annoying knowing such functionality exists, but you're not able to access it from C#. Fortunately, there are some easy workarounds one can use instead. Next time: filter handlers.

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  • Increasing deadlocks with NoLock

    - by Dave Ballantyne
    One on my personnel pet issues is with inappropriate use of the NOLOCK hint (and read uncommitted) .  Dont get me wrong, I have used it in exceptional circumstances , but as a general statement it is a bad thing.  Mostly , when NOLOCK, is used the discussion is around a single statement,  “it runs faster with nolock for XYZ reason”,  however ,IMO, this is quite a shorted sighted view.  What about the Transaction ? What about other concurrent users ?  What is good for one statement in isolation , does not mean that it is good for the system as a whole.  I have seen on a number of occasions deadlocks happen, when tasks that would of(and should of) be blocked continue to execute, only for a deadlock to occur at a later data writing (INSERT,UPDATE,DELETE) statement.  Writers will block writers regardless of isolation level. By Way of (fairly contrived ) example , lets generate some dummy tables and populate with some data drop table a go drop table b go Create Table a ( col1 integer ) go insert into a values(1) insert into a values(2) go Create Table b ( col1 integer ) go insert into b values(1) insert into b values(2) go   Now make two connections. In connection one execute set transaction isolation level read committed BEGIN TRAN Select * from a Select * from b delete from a In connection two execute set transaction isolation level read committed BEGIN TRAN Select * from a Select * from b delete from b Right now the ‘select from a’ in connection two is being blocked by the ‘delete from a’ in connection one.  This is ,IMO, quite a healthy and natural thing to be happening , some see this as a ‘slow down’, a drop in performance.  So, lets reach for our ‘NOLOCK’ magic pill.  Cancel the blocked query and ROLLBACK both transactions, then in connection one execute set transaction isolation level read uncommitted BEGIN TRAN Select * from a Select * from b delete from b and then in connection two execute set transaction isolation level read uncommitted BEGIN TRAN Select * from a Select * from b delete from a We have now solved out performance problem , no more blocking.  Lets finish the work required by the transaction, in connection one , execute delete from a Oh, ‘ performance problem’ again , its now being blocked. Still, lets complete the work in connection two…. delete from b DEADLOCK!!  It is important to be clear about the role of the select statements.  They do not participate within the deadlock, but are preventing code executing that would of.   Additionally, without the select readers to block, a deadlock would occur on the deletes with READ COMMITTED. Naturally, other isolation levels will exhibit different behaviour as to where and when they will and wont block,  and I would encourage you to read BOL and satisfy yourself that you really do NEED to NOLOCK.

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  • Executing server validators first before OnClientClick Javascript confirm/alert

    - by kaushalparik27
    I got to answer a simple question over community forums. Consider this: Suppose you are developing a webpage with few input controls and a submit button. You have placed some server validator controls like RequiredFieldValidator to validate the inputs entered by the user. Once user fill-in all the details and try to submit the page via button click you want to alert/confirm the submission like "Are you sure to modify above details?". You will consider to use javascript on click of the button.Everything seems simple and you are almost done. BUT, when you run the page; you will see that Javascript alert/confirm box is executing first before server validators try to validate the input controls! Well, this is expected behaviour. BUT, this is not you want. Then? The simple answer is: Call Page_ClientValidate() in javascript where you are alerting the submission. Below is the javascript example:    <script type="text/javascript" language="javascript">        function ValidateAllValidationGroups() {            if (Page_ClientValidate()) {                return confirm("Are you sure to modify above details?");            }        }    </script>Page_ClientValidate() function tests for all server validators and return bool value depends on whether the page meets defined validation criteria or not. In above example, confirm alert will only popup up if Page_ClientValidate() returns true (if all validations satisfy). You can also specify ValidationGroup inside this function as Page_ClientValidate('ValidationGroup1') to only validate a specific group of validation in your page.        function ValidateSpecificValidationGroup() {            if (Page_ClientValidate('ValidationGroup1')) {                return confirm("Are you sure to modify above details?");            }        }I have attached a sample example with this post here demonstrating both above cases. Hope it helps./.

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  • New Slides - and a discussion about Dictionary Statistics

    - by Mike Dietrich
    First of all we have just upoaded a new version of the Upgrade and Migration Workshop slides with some added information. So please feel free to download them from here.The slides have one new interesting information which lead to a discussion I've had in the past days with a very large customer regarding their upgrades - and internally on the mailing list targeting an EBS database upgrade from Oracle 10.2 to Oracle 11.2. Why are we creating dictionary statistics during upgrade? I'd believe this forced dictionary statistics creation got introduced with the desupport of the Rule Based Optimizer in Oracle 10g. The goal: as RBO is not supported anymore we have to make sure that the data dictionary has fresh and non-stale statistics. Actually that would have led in Oracle 9i to strange behaviour in some databases - so in Oracle 9i this was strongly disrecommended. The upgrade scripts got hardcoded to create these stats. But during tests we had the following findings: It's important to create dictionary statistics the night before the upgrade. Not two weeks before, not 60 minutes before your downtime begins. But very close to the upgrade. From Oracle 10g onwards you'd just say: $ execute DBMS_STATS.GATHER_DICTIONARY_STATS; This is important to make sure you have fresh dictionary statistics during upgrade for performance reasons. Tests have shown that running an upgrade without valid dictionary statistics might slow down the whole upgrade by factors of 2x-3x. And it would be also a great idea post upgrade to create again fresh dictionary statistics when you've did suppress the stats creation during the upgrade process. Suppress? Yes, you could set this underscore parameter in the init.ora: _optim_dict_stats_at_db_cr_upg=FALSE to suppress the forced dictionary statistics collection during an upgrade. We believe strongly that (a) people using the default statistics creation process which will create dictionary statistics by default and (b) create fresh stats before upgrade on the dictionary. Therefore we find it save once you have followed our advice to use the underscore during upgrade. And we've taken out that forced statistics collection during upgrade in the next release of the database. Please note: If you are using the DBUA for the upgrade it will remove underscore parameters for the upgrade run to improve performance - which is generally a good idea. So you'll have to start the DBUA with that call: $ dbua -initParam "_optim_dict_stats_at_cb_cr_upg"=FALSE -Mike

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  • How to debug lag using Bluetooth connected mouse and A2DP headset?

    - by gertvdijk
    I own a Logitech M555b mouse (since a week) for use with my HP Elitebook 8570w laptop running Kubuntu 12.04. Works fine right after connecting using the KDE Bluetooth control module. However, after some time (seemingly random), it starts to lag. Movements are being delayed for roughly 500ms for a short period of time. Usually it recovers after some time too, but it can take minutes. All actions are being delayed: movements, click, scrolls. Additionally, the movements can be choppy during these times. A workaround that always works for the same short period of time is to disconnect an re-connect the mouse. This can be done using the same KDE Bluetooth control module. What did I try already? Running this at boot time: echo on > `readlink -f /sys/class/bluetooth/hci0`/../../../power/level To disable any power saving features on the Bluetooth hci0 device. Check the mouse's batteries (it's just a week old, other new batteries: same result) Checking logs and kernel messages about Bluetooth-related entries: none aside the expected messages on connect time. I'm running kernel 3.5.0-13-generic as provided in the xorg-edgers PPA. Booting the regular 3.2 Precise kernel results in the same behaviour. Some other information that may help: It happens when no other Bluetooth connections are active on the machine. Similar symptoms also occur on my Bluetooth stereo (A2DP) headset, but then it's audio lagging and skipping. Swapping Bluetooth profiles as described here then helps. Conclusion: it's not the mouse that's faulty. The headset always worked fine using my now dead Thinkpad T61p with built-in Bluetooth. The bluetooth module in my laptop is connected via USB and shows up as Bus 002 Device 003: ID 0a5c:21e1 Broadcom Corp. I'm mobile and several people around me are using Bluetooth at work (A2DP mostly). It also occurs at home, where my neighbours are probably using Bluetooth as well. It could just be radio interference, but I think Bluetooth connections should just hop to another channel. And, moreover, it just works properly instantly when re-connecting. Therefore I think it's a software driver issue and I'd like to debug it. Is there any way to get more verbose logging on the Bluetooth(-hid) modules?

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  • How to build a 4x game?

    - by Marco
    I'm trying to study how succefully implement a 4x game. Area of interest: 1) map data: how to store stellars systems (graphs?), how to generate them and so on.. 2) multiplayer: how to organize code in a non graphical server and a client to display it 3) command system: what are patters to catch user and ai decisions and handle them, adding at first "explore" and "colonize" then "combat", "research", "spy" and so on (commands can affect ships, planets, research, etc..) 4) ai system: ai can use commands to expand, upgrade planets and ship I know is a big questions, so help is appreciated :D 1) Map data Best choice is have a graph to model a galaxy. A node is a stellar system and every system have a list of planets. Ship cannot travel outside of predefined paths, like in Ascendancy: http://www.abandonia.com/files/games/221/Ascendancy_2.png Every connection between two stellar systems have a cost, in turns. Generate a galaxy is only a matter of: - dimension: number of stellar systems, - variety: randomize number of planets and types (desertic, earth, etc..), - positions of each stellar system on game space - connections: assure that exist a path between every node, so graph is "connected" (not sure if this a matematically correct term) 2) Multiplayer Game is organized in turns: player 1, player 2, ai1, ai2. Server take care of all data and clients just diplay it and collect data change. Because is a turn game, latency is not a problem :D 3) Command system I would like to design a hierarchy of commands to take care of this aspect: abstract Genericcommand (target) ExploreCommand (Ship) extends genericcommand colonizeCommand (Ship) buildcommand(planet, object) and so on. In my head all this commands are stored in a queue for every planets, ships or reasearch center or spy, and each turn a command is sent to a server to apply command and change data state 4) ai system I don't have any idea about this. Is a big topic and what I want is a simple ai. Something like "expand and fight against everyone". I think about a behaviour tree to control ai moves, so I can develop an ai that try to build ships to expand and then colonize planets, upgrade them throught science and combat enemies. Could be done with a finite state machine too ? any ideas, resources, article are welcome!

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  • Regular Expression Transformation

    The regular expression transformation exposes the power of regular expression matching within the pipeline. One or more columns can be selected, and for each column an individual expression can be applied. The way multiple columns are handled can be set on the options page. The AND option means all columns must match, whilst the OR option means only one column has to match. If rows pass their tests then rows are passed down the successful match output. Rows that fail are directed down the alternate output. This transformation is ideal for validating data through the use of regular expressions. You can enter any expression you like, or select a pre-configured expression within the editor. You can expand the list of pre-configured expressions yourself. These are stored in a Xml file, %ProgramFiles%\Microsoft SQL Server\nnn\DTS\PipelineComponents\RegExTransform.xml, where nnn represents the folder version, 90 for 2005, 100 for 2008 and 110 for 2012. If you want to use regular expressions to manipulate data, rather than just validating it, try the RegexClean Transformation. The component is provided as an MSI file, however for 2005/200 you will have to add the transformation to the Visual Studio toolbox by hand. This process has been described in detail in the related FAQ entry for How do I install a task or transform component?, just select Regular Expression Transformation in the Choose Toolbox Items window. Downloads The Regular Expression Transformation is available for SQL Server 2005, SQL Server 2008 (includes R2) and SQL Server 2012. Please choose the version to match your SQL Server version, or you can install multiple versions and use them side by side if you have more than one version of SQL Server installed. Regular Expression Transformation for SQL Server 2005 Regular Expression Transformation for SQL Server 2008 Regular Expression Transformation for SQL Server 2012 Version History SQL Server 2012Version 2.0.0.87 - SQL Server 2012 release. Includes upgrade support for both 2005 and 2008 packages to 2012. (5 Jun 2012) SQL Server 2008Version 2.0.0.87 - Release for SQL Server 2008 Integration Services. (10 Oct 2008) SQL Server 2005 Version 1.1.0.93 - Added option for you to choose AND or OR logic when multiple columns have been selected. Previously behaviour was OR only. (31 Jul 2008) Version 1.0.0.76 - Installer update and improved exception handling. (28 Jan 2008) Version 1.0.0.41 - Update for user interface stability fixes. (2 Aug 2006) Version 1.0.0.24 - SQL Server 2005 RTM Refresh. SP1 Compatibility Testing. (12 Jun 2006) Version 1.0.0.9 - Public Release for SQL Server 2005 IDW 15 June CTP (29 Aug 2005) Screenshots  

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  • Where can I hire local programmers with very specific skillsets?

    - by Lostsoul
    I have been browsing the site and haven't found a exact fit to this question so I'll post it but if its already answered(since I'm sure its a common problem, then let me know). I have a business and want to create a totally different product in a different industry than I'm currently in, so I learned how to program and created a working prototype. I have a bit of savings and am getting some cash flow from my current business so I can go out and hire a developer(in the future hopefully it can be permenant but right now I just need a person willing to work on contract and code on weekends or their spare time and I just want to pay in cash instead of equity or future promises). At first I wasn't sure what kind of developer to hire but this question helped me understand I should target specific skills I need as opposed to general programmers. This poses a problem for me since general programmers are everywhere but if I want specific skills I'm unsure how to get them. I thought about a list of approaches but it doesn't feel complete or effective since it seems to be assuming good developers are actively looking. If it helps I want someone local(since this is my first developer hire) and looking for skills like cuda, hadoop, hbase, java and c. Any suggestions? As a FYI, I have been thinking of approaching it as: Go to meet ups for one or more skills I need. Use LinkedIn to find people with the skills I need Search for job postings that contain skills I need and then use linkedIn to reach out to that firms employees since many profiles on linkedin are not very updated or detailed but job postings generally are. Send postings to universities and maybe find a student who loves technology so much they learned these tools on their own. Post on job board. Not sure how successful it will be to post to monster. Use Craigslist, not sure if a highly skilled developer would go here for work. What am I missing? I could be wrong but it seems like good/smart/able developers aren't hunting for work non-stop(especially in this tech job market). Plus most successful people I know have work/life balance so I'm not sure if the best ones really care about code after work. Lastly, most of the skills I need aren't used in big corporations so not sure how aggressively smart developers at small shops look for work. I don’t really know any developers personally, so but should I be using the above plan or if they live balanced lives should I be looking outside of the regular resources(and instead focus on asking around my gym or my accountant or something)? Sorry, I'm making huge assumptions here, I guess because developers are a total mystery to me. I kind of wish Jane Goodall wrote a book on understanding developers social behaviour better :-p

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  • Thinkpad brightness steps error using FN+Home/End

    - by petermolnar
    I've met the following problem: normally my T400 (Lenovo Thinkpad) has 16 steps of brightness, and Windows utilizes it correctly. After a fresh install & minor tweaks Mint 12 (which is based on 11.10 Ubuntu) I only had 6 steps which was way to few. Listing /sys/class/backlight showed 3 entried. I removed the acpi-tools package, one of the disapperared - and I now have 10 steps! Therefore I think if I can reduce the entries to 1 I'm going to have 16 steps, since the stepping will be 1 instead of 2 (or 3). /sys/class/backlight/ intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight thinkpad_screen -> ../../devices/virtual/backlight/thinkpad_screen The problem is that I'm unable to trace back what are the configs / daemons / kernel options triggers these two. More strangely, I discovered a strange behaviour. I monitored watch -n1 "cat /sys/class/backlight/thinkpad_screen/actual_brightness" and watch -n1 "cat /sys/class/backlight/intel_backlight/actual_brightness" while changing the brightness with FN+home/end combinations from max to min. The outcome is the following: brighness intel thinkpad --------- ----- -------- MAX 2408475 7 | 1955115 5 | 1435640 3 | 1246740 1 | 1086175 0 | 1010615 6 | 859495 4 | 689485 2 v 481695 0 MIN 217235 0 brighness intel thinkpad --------- ----- -------- MIN 217235 0 | 481695 2 | 689485 4 | 859495 6 | 1010615 7 | 1086175 1 | 1246740 3 | 1435640 5 v 1955115 7 MAX 2408475 0 When stepping from MIN to MAX, there's no difference between the last 2 steps. Also, the OSD icon (Cinnamon desktop, default theme) goes from full to min in 4 steps and from full to min once again in 4 steps. So... it seems that the intel entry is working correctly, showing correct values. The thinkpad entry however twists the things and even showing incorrect values. Does anyone have any idea how to get rid of the thinkpad entry? System data: Linux Mint 12 3.0.0-16 kernel Lenovo ThinkPad T400 Cinnamon 1.4 desktop For any additional info, please tell me what do you need. EDIT I'm sorry, I forgot to mention, I added acpi_backlight=vendor to GRUB cmdline as well, this is the result of the semi-better working than the default.

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  • A brief note for customers running SOA Suite on AIX platforms

    - by christian
    When running Oracle SOA Suite with IBM JVMs on the AIX platform, we have seen performance slowdowns and/or memory leaks. On occasion, we have even encountered some OutOfMemoryError conditions and the concomittant Java coredump. If you are experiencing this issue, the resolution may be to configure -Dsun.reflect.inflationThreshold=0 in your JVM startup parameters. https://www.ibm.com/developerworks/java/library/j-nativememory-aix/ contains a detailed discussion of the IBM AIX JVM memory model, but I will summarize my interpretation and understanding of it in the context of SOA Suite, below. Java ClassLoaders on IBM JVMs are allocated a native memory area into which they are anticipated to map such things as jars loaded from the filesystem. This is an excellent memory optimization, as the file can be loaded into memory once and then shared amongst many JVMs on the same host, allowing for excellent horizontal scalability on AIX hosts. However, Java ClassLoaders are not used exclusively for loading files from disk. A performance optimization by the Oracle Java language developers enables reflectively accessed data to optimize from a JNI call into Java bytecodes which are then amenable to hotspot optimizations, amongst other things. This performance optimization is called inflation, and it is executed by generating a sun.reflect.DelegatingClassLoader instance dynamically to inject the Java bytecode into the virtual machine. It is generally considered an excellent optimization. However, it interacts very negatively with the native memory area allocated by the IBM JVM, effectively locking out memory that could otherwise be used by the Java process. SOA Suite and WebLogic are both very large users of reflection code. They reflectively use many code paths in their operation, generating lots of DelegatingClassLoaders in normal operation. The IBM JVM slowdown and subsequent OutOfMemoryError are as a direct result of the Java memory consumed by the DelegatingClassLoader instances generated by SOA Suite and WebLogic. Java garbage collection runs more frequently to try and keep memory available, until it can no longer do so and throws OutOfMemoryError. The setting sun.reflect.inflationThreshold=0 disables this optimization entirely, never allowing the JVM to generate the optimized reflection code. IBM JVMs are susceptible to this issue primarily because all Java ClassLoaders have this native memory allocation, which is shared with the regular Java heap. Oracle JVMs don't automatically give all ClassLoaders a native memory area, and my understanding is that jar files are never mapped completely from shared memory in the same way as IBM does it. This results in different behaviour characteristics on IBM vs Oracle JVMs.

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  • How to remove the boundary effects arising due to zero padding in scipy/numpy fft?

    - by Omkar
    I have made a python code to smoothen a given signal using the Weierstrass transform, which is basically the convolution of a normalised gaussian with a signal. The code is as follows: #Importing relevant libraries from __future__ import division from scipy.signal import fftconvolve import numpy as np def smooth_func(sig, x, t= 0.002): N = len(x) x1 = x[-1] x0 = x[0] # defining a new array y which is symmetric around zero, to make the gaussian symmetric. y = np.linspace(-(x1-x0)/2, (x1-x0)/2, N) #gaussian centered around zero. gaus = np.exp(-y**(2)/t) #using fftconvolve to speed up the convolution; gaus.sum() is the normalization constant. return fftconvolve(sig, gaus/gaus.sum(), mode='same') If I run this code for say a step function, it smoothens the corner, but at the boundary it interprets another corner and smoothens that too, as a result giving unnecessary behaviour at the boundary. I explain this with a figure shown in the link below. Boundary effects This problem does not arise if we directly integrate to find convolution. Hence the problem is not in Weierstrass transform, and hence the problem is in the fftconvolve function of scipy. To understand why this problem arises we first need to understand the working of fftconvolve in scipy. The fftconvolve function basically uses the convolution theorem to speed up the computation. In short it says: convolution(int1,int2)=ifft(fft(int1)*fft(int2)) If we directly apply this theorem we dont get the desired result. To get the desired result we need to take the fft on a array double the size of max(int1,int2). But this leads to the undesired boundary effects. This is because in the fft code, if size(int) is greater than the size(over which to take fft) it zero pads the input and then takes the fft. This zero padding is exactly what is responsible for the undesired boundary effects. Can you suggest a way to remove this boundary effects? I have tried to remove it by a simple trick. After smoothening the function I am compairing the value of the smoothened signal with the original signal near the boundaries and if they dont match I replace the value of the smoothened func with the input signal at that point. It is as follows: i = 0 eps=1e-3 while abs(smooth[i]-sig[i])> eps: #compairing the signals on the left boundary smooth[i] = sig[i] i = i + 1 j = -1 while abs(smooth[j]-sig[j])> eps: # compairing on the right boundary. smooth[j] = sig[j] j = j - 1 There is a problem with this method, because of using an epsilon there are small jumps in the smoothened function, as shown below: jumps in the smooth func Can there be any changes made in the above method to solve this boundary problem?

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  • Building SANE from git-source produce backend missmatch on 12.04 even if built locally

    - by deinonychusaur
    It seems to me that with Ubuntu Precise Pangolin it is all but easy to do a proper install of SANE from source (git-repo). I've found other scanning issues trying to find an answer to this, where the output people posted seems to indicate they suffer the same issue (unknowingly). If I run on a fresh install of Ubuntu 12.04 with compiled SANE source from the git I get: $ scanimage -V scanimage (sane-backends) 1.0.24git; backend version 1.0.22 (I basically followed the instructions on http://ubuntuportal.com/2012/02/how-to-get-an-canon-canoscan-lide-100-scanner-to-work-in-ubuntu-11-10linux-mint-12.html since I didn't find any other information making sure that sane was not installed prior to installation.) My primary interest is the epson2-backend. In 1.0.22 it offers the wrong TPU settings for Epson V700 (TPU2-mode wasn't supported in 1.0.22, and the scanner is useless to me if I don't have the TPU2-support). Since if I ask it to enter transparency mode, it shows 1.0.22 behaviour, it implies that the epson2-backend comes from 1.0.22 and not 1.0.24 even though I just built it. If I install SANE with prefix to a local folder and run that version of scanimage it still produces the mismatch. However, on another computer where I installed a custom 1.0.22 build of SANE prior to upgrading to Ubuntu 12.04, I can build and install the same SANE-git locally and have it correctly match backends: $ ./SANE/bin/scanimage -V scanimage (sane-backends) 1.0.24git; backend version 1.0.24 $ scanimage -V scanimage (sane-backends) 1.0.22; backend version 1.0.22 On this computer the 1.0.24 works correctly in finding TPU2 on Epson V700. So what am I missing/doing wrong? (And I want to replace 1.0.22 with 1.0.24 for the whole system, the local build was just debugging.) Any help would be much appreciated. Edit 1: Just tried compiling SANE using this instruction on Ubuntu 10.04 and it worked like a charm. However, when I upgraded to 12.04 (really would like to run 12.04), SANE was downgraded to 1.0.22. When trying the same set of instructions on 12.04 I was still out of luck -- the backend missmatch was there again (and I do have libusb-dev installed) Edit 2: I updated to Ubuntu 12.10 which now has the 1.0.23 SANE drivers. I haven't dared trying to compile from source on 12.10 since 1.0.23 is good enough for me. This is just a work-around and I would still like to know what's up with Ubuntu 12.04.

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  • Lenovo Thinkpad X1 Carbon support

    - by Robottinosino
    I am considering selling my Mac to get money towards a Lenovo Thinkpad X1 because what I really want to do is to be running an Ubuntu system all the time. Is this machine completely supported in Ubuntu, with no tiny little feature missing just because I am "going Linux"? Optional user story section, skip to the question below if you don't have time: I have a friend who bought a "works on Ubuntu" system a year ago and has hated the fact ever since: battery lasts less than if he boots in Windows (which he despises) and he ascribes that to "no good OS/harware integration and support for advanced chipset power management features", odd behaviour on suspend/resume/hibernate (says: "when it works 90% of the time and the other 10% it makes you lose your work is as good as broken - 90% is the same as 0% he says), some occasional graphics card glitches he can perfectly well live with and has almost grown affectionate to, and finally, and that is what would make him undo his choice if he could, bad "input device drivers". He says: trackpoint and trackpad just "feel different", "so much better" on Windows and that was impossible to know from the website brochure. That story makes me very doubtful... but I want to abandon this "walled garden" of prison that is my Mac and go Ubuntu all the way, no doubt about that! My dilemma at this time is just: "I don't want to live with those eternal frustrations for sure"! Here's a directly answerable phrasing of my question: Is the Lenovo Thinkpad X1 supported on Ubuntu? Yes/no, which version? Which hardware features are not supported? Provide a list Optionally: sort the list in descending order of frustration from your experience Optionally: mention if there are acceptable workarounds to the "out-of-the-box" condition described in the earlier points and whether this ameliorates frustration at least to "tolerable" levels Comment: the Ubuntu hardware certification page is so not-for-end-users it's unreal. Whoa. What would make it end-user friendly is: Link to "buy here and you'll be just fine, this is the right configuration for you, it'll work as long as you press BUY on that page and don't browse further" Remove mentions of may and might not work. Just tell it straight: press buy here and you will get a working system with the exception of A, B, C (so that I can decide whether the philosophical "freedom pleasure" I get from escaping an Apple world is enough to off-balance the loss, for instance, of Bluetooth capabilities (something that I of course use on my Mac) but "could" lose to use free (as in freedom) software The certification page fails to dispel doubts in me as an end-user. I don't feel "eased into Ubuntu", I feel "partially informed".

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  • SQL 2014 does data the way developers want

    - by Rob Farley
    A post I’ve been meaning to write for a while, good that it fits with this month’s T-SQL Tuesday, hosted by Joey D’Antoni (@jdanton) Ever since I got into databases, I’ve been a fan. I studied Pure Maths at university (as well as Computer Science), and am very comfortable with Set Theory, which undergirds relational database concepts. But I’ve also spent a long time as a developer, and appreciate that that databases don’t exactly fit within the stuff I learned in my first year of uni, particularly the “Algorithms and Data Structures” subject, in which we studied concepts like linked lists. Writing in languages like C, we used pointers to quickly move around data, without a database in sight. Of course, if we had a power failure all this data was lost, as it was only persisted in RAM. Perhaps it’s why I’m a fan of database internals, of indexes, latches, execution plans, and so on – the developer in me wants to be reassured that we’re getting to the data as efficiently as possible. Back when SQL Server 2005 was approaching, one of the big stories was around CLR. Many were saying that T-SQL stored procedures would be a thing of the past because we now had CLR, and that obviously going to be much faster than using the abstracted T-SQL. Around the same time, we were seeing technologies like Linq-to-SQL produce poor T-SQL equivalents, and developers had had a gutful. They wanted to move away from T-SQL, having lost trust in it. I was never one of those developers, because I’d looked under the covers and knew that despite being abstracted, T-SQL was still a good way of getting to data. It worked for me, appealing to both my Set Theory side and my Developer side. CLR hasn’t exactly become the default option for stored procedures, although there are plenty of situations where it can be useful for getting faster performance. SQL Server 2014 is different though, through Hekaton – its In-Memory OLTP environment. When you create a table using Hekaton (that is, a memory-optimized one), the table you create is the kind of thing you’d’ve made as a developer. It creates code in C leveraging structs and pointers and arrays, which it compiles into fast code. When you insert data into it, it creates a new instance of a struct in memory, and adds it to an array. When the insert is committed, a small write is made to the transaction to make sure it’s durable, but none of the locking and latching behaviour that typifies transactional systems is needed. Indexes are done using hashes and using bw-trees (which avoid locking through the use of pointers) and by handling each updates as a delete-and-insert. This is data the way that developers do it when they’re coding for performance – the way I was taught at university before I learned about databases. Being done in C, it compiles to very quick code, and although these tables don’t support every feature that regular SQL tables do, this is still an excellent direction that has been taken. @rob_farley

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