Search Results

Search found 10860 results on 435 pages for 'bad blocks'.

Page 206/435 | < Previous Page | 202 203 204 205 206 207 208 209 210 211 212 213  | Next Page >

  • USB drives not recognized all of a sudden (module usb_storage not loading)

    - by Siddharth
    I am very close to the solution, just need to know how to get usb-storage to load I have tried most of the advice on askubuntu and other sites, usb_storage enable to fdisk -l. But I am unable to find steps to get it working again. sudo lsusb results Bus.... skipped 4 lines Bus 004 Device 002: ID 413c:3012 Dell Computer Corp. Optical Wheel Mouse Bus 005 Device 002: ID 413c:2105 Dell Computer Corp. Model L100 Keyboard Bus 001 Device 005: ID 8564:1000 sudo dmseg | tail reports [ 69.567948] usb 1-4: USB disconnect, device number 4 [ 74.084041] usb 1-6: new high-speed USB device number 5 using ehci_hcd [ 74.240484] Initializing USB Mass Storage driver... [ 74.256033] scsi5 : usb-storage 1-6:1.0 [ 74.256145] usbcore: registered new interface driver usb-storage [ 74.256147] USB Mass Storage support registered. [ 74.257290] usbcore: deregistering interface driver usb-storage fdisk -l reports Device Boot Start End Blocks Id System /dev/sda1 * 2048 972656639 486327296 83 Linux /dev/sda2 972658686 976771071 2056193 5 Extended /dev/sda5 972658688 976771071 2056192 82 Linux swap / Solaris I think I need steps to install and get usb_storage module working. Edit : I tried sudo modprobe -v usb-storage reports sudo modprobe -v usb-storage insmod /lib/modules/3.2.0-48-generic-pae/kernel/drivers/usb/storage/usb-storage.ko Edit : jsiddharth@siddharth-desktop:~$ sudo udevadm monitor --udev monitor will print the received events for: UDEV - the event which udev sends out after rule processing UDEV [4757.144372] add /module/usb_storage (module) UDEV [4757.146558] remove /module/usb_storage (module) UDEV [4757.148707] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6 (usb) UDEV [4757.149699] add /bus/usb/drivers/usb-storage (drivers) UDEV [4757.151214] remove /bus/usb/drivers/usb-storage (drivers) UDEV [4757.156873] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0 (usb) UDEV [4757.160903] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9 (scsi) UDEV [4757.164672] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9/scsi_host/host9 (scsi_host) UDEV [4757.165163] remove /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9/scsi_host/host9 (scsi_host) UDEV [4757.165440] remove /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9 (scsi) Narrowing down more : Seems like I need usb_storage to load as a module jsiddharth@siddharth-desktop:~$ lsmod | grep usb usbserial 37201 0 usbhid 41937 0 hid 77428 1 usbhid Still no usb driver mounted. Nor does a device show up in /dev. Any step by step process to debug and fix this will be really helpful.

    Read the article

  • Poll Results: Foreign Key Constraints

    - by Darren Gosbell
    A few weeks ago I did the following post asking people – if they used foreign key constraints in their star schemas. The poll is still open if you are interested in adding to it, but here is what the chart looks like as of today. (at the bottom of the poll itself there is a link to the live results, unfortunately I cannot link the live results in here as the blogging platform blocks the required javascript)   Interestingly the results are fairly even. Of the 78 respondents, fractionally over half at least aim to start with referential integrity in their star schemas. I did not want to influence the results by sharing my opinion, but my personal preference is to always aim to have foreign key constraints. But at the same time, I am pragmatic about it, I do have projects where for various reasons some constraints are not defined. And I also have other designs that I have inherited, where it would just be too much work to go back and add foreign key constraints. If you are going to implement foreign keys in your star schema, they really need to be there at the start. In fact this poll was was the result of a feature request for BIDSHelper asking for a feature to check for null/missing foreign keys and I am entirely convinced that BIDS is the wrong place for this sort of functionality. BIDS is a design tool, your data needs to be constantly checked for consistency. It's not that I think that it's impossible to get a design working without foreign key constraints, but I like the idea of failing as soon as possible if there is an error and enforcing foreign key constraints lets me "fail early" if there are constancy issues with my data. By far the biggest concern with foreign keys is performance and I suppose I'm curious as to how often people actually measure and quantify this. I worked on a project a number of years ago that had very large data volumes and we did find that foreign key constraints did have a measurable impact, but what we did was to disable the constraints before loading the data, then enabled and checked them afterwards. This saved as time (although not as much as not having constraints at all), but still let us know early in the process if there were any consistency issues. For the people that do not have consistent data, if you have ETL processes that you control that are building your star schema which you also control, then to be blunt you only have yourself to blame. It is the job of the ETL process to make the data consistent. There are techniques for handling situations like missing data as well as  early and late arriving data. Ralph Kimball's book – The Data Warehouse Toolkit goes through some design patterns for handling data consistency. Having foreign key relationships can also help the relational engine to optimize queries as noted in this recent blog post by Boyan Penev

    Read the article

  • Microsoft Introduces WebMatrix

    - by Rick Strahl
    originally published in CoDe Magazine Editorial Microsoft recently released the first CTP of a new development environment called WebMatrix, which along with some of its supporting technologies are squarely aimed at making the Microsoft Web Platform more approachable for first-time developers and hobbyists. But in the process, it also provides some updated technologies that can make life easier for existing .NET developers. Let’s face it: ASP.NET development isn’t exactly trivial unless you already have a fair bit of familiarity with sophisticated development practices. Stick a non-developer in front of Visual Studio .NET or even the Visual Web Developer Express edition and it’s not likely that the person in front of the screen will be very productive or feel inspired. Yet other technologies like PHP and even classic ASP did provide the ability for non-developers and hobbyists to become reasonably proficient in creating basic web content quickly and efficiently. WebMatrix appears to be Microsoft’s attempt to bring back some of that simplicity with a number of technologies and tools. The key is to provide a friendly and fully self-contained development environment that provides all the tools needed to build an application in one place, as well as tools that allow publishing of content and databases easily to the web server. WebMatrix is made up of several components and technologies: IIS Developer Express IIS Developer Express is a new, self-contained development web server that is fully compatible with IIS 7.5 and based on the same codebase that IIS 7.5 uses. This new development server replaces the much less compatible Cassini web server that’s been used in Visual Studio and the Express editions. IIS Express addresses a few shortcomings of the Cassini server such as the inability to serve custom ISAPI extensions (i.e., things like PHP or ASP classic for example), as well as not supporting advanced authentication. IIS Developer Express provides most of the IIS 7.5 feature set providing much better compatibility between development and live deployment scenarios. SQL Server Compact 4.0 Database access is a key component for most web-driven applications, but on the Microsoft stack this has mostly meant you have to use SQL Server or SQL Server Express. SQL Server Compact is not new-it’s been around for a few years, but it’s been severely hobbled in the past by terrible tool support and the inability to support more than a single connection in Microsoft’s attempt to avoid losing SQL Server licensing. The new release of SQL Server Compact 4.0 supports multiple connections and you can run it in ASP.NET web applications simply by installing an assembly into the bin folder of the web application. In effect, you don’t have to install a special system configuration to run SQL Compact as it is a drop-in database engine: Copy the small assembly into your BIN folder (or from the GAC if installed fully), create a connection string against a local file-based database file, and then start firing SQL requests. Additionally WebMatrix includes nice tools to edit the database tables and files, along with tools to easily upsize (and hopefully downsize in the future) to full SQL Server. This is a big win, pending compatibility and performance limits. In my simple testing the data engine performed well enough for small data sets. This is not only useful for web applications, but also for desktop applications for which a fully installed SQL engine like SQL Server would be overkill. Having a local data store in those applications that can potentially be accessed by multiple users is a welcome feature. ASP.NET Razor View Engine What? Yet another native ASP.NET view engine? We already have Web Forms and various different flavors of using that view engine with Web Forms and MVC. Do we really need another? Microsoft thinks so, and Razor is an implementation of a lightweight, script-only view engine. Unlike the Web Forms view engine, Razor works only with inline code, snippets, and markup; therefore, it is more in line with current thinking of what a view engine should represent. There’s no support for a “page model” or any of the other Web Forms features of the full-page framework, but just a lightweight scripting engine that works with plain markup plus embedded expressions and code. The markup syntax for Razor is geared for minimal typing, plus some progressive detection of where a script block/expression starts and ends. This results in a much leaner syntax than the typical ASP.NET Web Forms alligator (<% %>) tags. Razor uses the @ sign plus standard C# (or Visual Basic) block syntax to delineate code snippets and expressions. Here’s a very simple example of what Razor markup looks like along with some comment annotations: <!DOCTYPE html> <html>     <head>         <title></title>     </head>     <body>     <h1>Razor Test</h1>          <!-- simple expressions -->     @DateTime.Now     <hr />     <!-- method expressions -->     @DateTime.Now.ToString("T")          <!-- code blocks -->     @{         List<string> names = new List<string>();         names.Add("Rick");         names.Add("Markus");         names.Add("Claudio");         names.Add("Kevin");     }          <!-- structured block statements -->     <ul>     @foreach(string name in names){             <li>@name</li>     }     </ul>           <!-- Conditional code -->        @if(true) {                        <!-- Literal Text embedding in code -->        <text>         true        </text>;    }    else    {        <!-- Literal Text embedding in code -->       <text>       false       </text>;    }    </body> </html> Like the Web Forms view engine, Razor parses pages into code, and then executes that run-time compiled code. Effectively a “page” becomes a code file with markup becoming literal text written into the Response stream, code snippets becoming raw code, and expressions being written out with Response.Write(). The code generated from Razor doesn’t look much different from similar Web Forms code that only uses script tags; so although the syntax may look different, the operational model is fairly similar to the Web Forms engine minus the overhead of the large Page object model. However, there are differences: -Razor pages are based on a new base class, Microsoft.WebPages.WebPage, which is hosted in the Microsoft.WebPages assembly that houses all the Razor engine parsing and processing logic. Browsing through the assembly (in the generated ASP.NET Temporary Files folder or GAC) will give you a good idea of the functionality that Razor provides. If you look closely, a lot of the feature set matches ASP.NET MVC’s view implementation as well as many of the helper classes found in MVC. It’s not hard to guess the motivation for this sort of view engine: For beginning developers the simple markup syntax is easier to work with, although you obviously still need to have some understanding of the .NET Framework in order to create dynamic content. The syntax is easier to read and grok and much shorter to type than ASP.NET alligator tags (<% %>) and also easier to understand aesthetically what’s happening in the markup code. Razor also is a better fit for Microsoft’s vision of ASP.NET MVC: It’s a new view engine without the baggage of Web Forms attached to it. The engine is more lightweight since it doesn’t carry all the features and object model of Web Forms with it and it can be instantiated directly outside of the HTTP environment, which has been rather tricky to do for the Web Forms view engine. Having a standalone script parser is a huge win for other applications as well – it makes it much easier to create script or meta driven output generators for many types of applications from code/screen generators, to simple form letters to data merging applications with user customizability. For me personally this is very useful side effect and who knows maybe Microsoft will actually standardize they’re scripting engines (die T4 die!) on this engine. Razor also better fits the “view-based” approach where the view is supposed to be mostly a visual representation that doesn’t hold much, if any, code. While you can still use code, the code you do write has to be self-contained. Overall I wouldn’t be surprised if Razor will become the new standard view engine for MVC in the future – and in fact there have been announcements recently that Razor will become the default script engine in ASP.NET MVC 3.0. Razor can also be used in existing Web Forms and MVC applications, although that’s not working currently unless you manually configure the script mappings and add the appropriate assemblies. It’s possible to do it, but it’s probably better to wait until Microsoft releases official support for Razor scripts in Visual Studio. Once that happens, you can simply drop .cshtml and .vbhtml pages into an existing ASP.NET project and they will work side by side with classic ASP.NET pages. WebMatrix Development Environment To tie all of these three technologies together, Microsoft is shipping WebMatrix with an integrated development environment. An integrated gallery manager makes it easy to download and load existing projects, and then extend them with custom functionality. It seems to be a prominent goal to provide community-oriented content that can act as a starting point, be it via a custom templates or a complete standard application. The IDE includes a project manager that works with a single project and provides an integrated IDE/editor for editing the .cshtml and .vbhtml pages. A run button allows you to quickly run pages in the project manager in a variety of browsers. There’s no debugging support for code at this time. Note that Razor pages don’t require explicit compilation, so making a change, saving, and then refreshing your page in the browser is all that’s needed to see changes while testing an application locally. It’s essentially using the auto-compiling Web Project that was introduced with .NET 2.0. All code is compiled during run time into dynamically created assemblies in the ASP.NET temp folder. WebMatrix also has PHP Editing support with syntax highlighting. You can load various PHP-based applications from the WebMatrix Web Gallery directly into the IDE. Most of the Web Gallery applications are ready to install and run without further configuration, with Wizards taking you through installation of tools, dependencies, and configuration of the database as needed. WebMatrix leverages the Web Platform installer to pull the pieces down from websites in a tight integration of tools that worked nicely for the four or five applications I tried this out on. Click a couple of check boxes and fill in a few simple configuration options and you end up with a running application that’s ready to be customized. Nice! You can easily deploy completed applications via WebDeploy (to an IIS server) or FTP directly from within the development environment. The deploy tool also can handle automatically uploading and installing the database and all related assemblies required, making deployment a simple one-click install step. Simplified Database Access The IDE contains a database editor that can edit SQL Compact and SQL Server databases. There is also a Database helper class that facilitates database access by providing easy-to-use, high-level query execution and iteration methods: @{       var db = Database.OpenFile("FirstApp.sdf");     string sql = "select * from customers where Id > @0"; } <ul> @foreach(var row in db.Query(sql,1)){         <li>@row.FirstName @row.LastName</li> } </ul> The query function takes a SQL statement plus any number of positional (@0,@1 etc.) SQL parameters by simple values. The result is returned as a collection of rows which in turn have a row object with dynamic properties for each of the columns giving easy (though untyped) access to each of the fields. Likewise Execute and ExecuteNonQuery allow execution of more complex queries using similar parameter passing schemes. Note these queries use string-based queries rather than LINQ or Entity Framework’s strongly typed LINQ queries. While this may seem like a step back, it’s also in line with the expectations of non .NET script developers who are quite used to writing and using SQL strings in code rather than using OR/M frameworks. The only question is why was something not included from the beginning in .NET and Microsoft made developers build custom implementations of these basic building blocks. The implementation looks a lot like a DataTable-style data access mechanism, but to be fair, this is a common approach in scripting languages. This type of syntax that uses simple, static, data object methods to perform simple data tasks with one line of code are common in scripting languages and are a good match for folks working in PHP/Python, etc. Seems like Microsoft has taken great advantage of .NET 4.0’s dynamic typing to provide this sort of interface for row iteration where each row has properties for each field. FWIW, all the examples demonstrate using local SQL Compact files - I was unable to get a SQL Server connection string to work with the Database class (the connection string wasn’t accepted). However, since the code in the page is still plain old .NET, you can easily use standard ADO.NET code or even LINQ or Entity Framework models that are created outside of WebMatrix in separate assemblies as required. The good the bad the obnoxious - It’s still .NET The beauty (or curse depending on how you look at it :)) of Razor and the compilation model is that, behind it all, it’s still .NET. Although the syntax may look foreign, it’s still all .NET behind the scenes. You can easily access existing tools, helpers, and utilities simply by adding them to the project as references or to the bin folder. Razor automatically recognizes any assembly reference from assemblies in the bin folder. In the default configuration, Microsoft provides a host of helper functions in a Microsoft.WebPages assembly (check it out in the ASP.NET temp folder for your application), which includes a host of HTML Helpers. If you’ve used ASP.NET MVC before, a lot of the helpers should look familiar. Documentation at the moment is sketchy-there’s a very rough API reference you can check out here: http://www.asp.net/webmatrix/tutorials/asp-net-web-pages-api-reference Who needs WebMatrix? Uhm… good Question Clearly Microsoft is trying hard to create an environment with WebMatrix that is easy to use for newbie developers. The goal seems to be simplicity in providing a minimal development environment and an easy-to-use script engine/language that makes it easy to get started with. There’s also some focus on community features that can be used as starting points, such as Web Gallery applications and templates. The community features in particular are very nice and something that would be nice to eventually see in Visual Studio as well. The question is whether this is too little too late. Developers who have been clamoring for a simpler development environment on the .NET stack have mostly left for other simpler platforms like PHP or Python which are catering to the down and dirty developer. Microsoft will be hard pressed to win those folks-and other hardcore PHP developers-back. Regardless of how much you dress up a script engine fronted by the .NET Framework, it’s still the .NET Framework and all the complexity that drives it. While .NET is a fine solution in its breadth and features once you get a basic handle on the core features, the bar of entry to being productive with the .NET Framework is still pretty high. The MVC style helpers Microsoft provides are a good step in the right direction, but I suspect it’s not enough to shield new developers from having to delve much deeper into the Framework to get even basic applications built. Razor and its helpers is trying to make .NET more accessible but the reality is that in order to do useful stuff that goes beyond the handful of simple helpers you still are going to have to write some C# or VB or other .NET code. If the target is a hobby/amateur/non-programmer the learning curve isn’t made any easier by WebMatrix it’s just been shifted a tad bit further along in your development endeavor when you run out of canned components that are supplied either by Microsoft or the community. The database helpers are interesting and actually I’ve heard a lot of discussion from various developers who’ve been resisting .NET for a really long time perking up at the prospect of easier data access in .NET than the ridiculous amount of code it takes to do even simple data access with raw ADO.NET. It seems sad that such a simple concept and implementation should trigger this sort of response (especially since it’s practically trivial to create helpers like these or pick them up from countless libraries available), but there it is. It also shows that there are plenty of developers out there who are more interested in ‘getting stuff done’ easily than necessarily following the latest and greatest practices which are overkill for many development scenarios. Sometimes it seems that all of .NET is focused on the big life changing issues of development, rather than the bread and butter scenarios that many developers are interested in to get their work accomplished. And that in the end may be WebMatrix’s main raison d'être: To bring some focus back at Microsoft that simpler and more high level solutions are actually needed to appeal to the non-high end developers as well as providing the necessary tools for the high end developers who want to follow the latest and greatest trends. The current version of WebMatrix hits many sweet spots, but it also feels like it has a long way to go before it really can be a tool that a beginning developer or an accomplished developer can feel comfortable with. Although there are some really good ideas in the environment (like the gallery for downloading apps and components) which would be a great addition for Visual Studio as well, the rest of the development environment just feels like crippleware with required functionality missing especially debugging and Intellisense, but also general editor support. It’s not clear whether these are because the product is still in an early alpha release or whether it’s simply designed that way to be a really limited development environment. While simple can be good, nobody wants to feel left out when it comes to necessary tool support and WebMatrix just has that left out feeling to it. If anything WebMatrix’s technology pieces (which are really independent of the WebMatrix product) are what are interesting to developers in general. The compact IIS implementation is a nice improvement for development scenarios and SQL Compact 4.0 seems to address a lot of concerns that people have had and have complained about for some time with previous SQL Compact implementations. By far the most interesting and useful technology though seems to be the Razor view engine for its light weight implementation and it’s decoupling from the ASP.NET/HTTP pipeline to provide a standalone scripting/view engine that is pluggable. The first winner of this is going to be ASP.NET MVC which can now have a cleaner view model that isn’t inconsistent due to the baggage of non-implemented WebForms features that don’t work in MVC. But I expect that Razor will end up in many other applications as a scripting and code generation engine eventually. Visual Studio integration for Razor is currently missing, but is promised for a later release. The ASP.NET MVC team has already mentioned that Razor will eventually become the default MVC view engine, which will guarantee continued growth and development of this tool along those lines. And the Razor engine and support tools actually inherit many of the features that MVC pioneered, so there’s some synergy flowing both ways between Razor and MVC. As an existing ASP.NET developer who’s already familiar with Visual Studio and ASP.NET development, the WebMatrix IDE doesn’t give you anything that you want. The tools provided are minimal and provide nothing that you can’t get in Visual Studio today, except the minimal Razor syntax highlighting, so there’s little need to take a step back. With Visual Studio integration coming later there’s little reason to look at WebMatrix for tooling. It’s good to see that Microsoft is giving some thought about the ease of use of .NET as a platform For so many years, we’ve been piling on more and more new features without trying to take a step back and see how complicated the development/configuration/deployment process has become. Sometimes it’s good to take a step - or several steps - back and take another look and realize just how far we’ve come. WebMatrix is one of those reminders and one that likely will result in some positive changes on the platform as a whole. © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET   IIS7  

    Read the article

  • Voxel Engine in Multiplayer?

    - by Oliver Schöning
    This is a question more out of Interest for now, because I am not even near to the point that I could create this project at the moment. I really like the progress on the Atomontage Engine. A Voxel engine that is WIP at the moment. I would like to create a Voxel SERVER eventually. First in JavaScript (That's what I am learning right now) later perhaps in C++ for speed. Remember, I am perfectly aware that this is very hard! This is a brainstorm for the next 10 years as for now. What I would like to achieve one day is a Multiplayer Game in the Browser where the voxels positions are updated by XYZ input from the server. The Browser Does only 3 things: sending player input to the server, updating Voxel positions send from the server and rendering the world. I imagine using something like the Three.js libary on the client side. So that would be my programming dream right there... Now to something simpler for the near future. Right now I am learning javascript. And I am making games with Construct2. (A really cool JavaScript "game maker") The plan is to create a 2D Voxel enviorment (Block Voxels) on the Socket.IO Server* and send the position of the Voxels and Players to the Client side which then positions the Voxel Blocks to the Server Output coordinates. I think that is a bit more manageable then the other bigger idea. And also there should be no worries about speed with this type of project in JavaScript (I hope). Extra Info: *I am using nodejs (Without really knowing what it does besides making Socket.IO work) So now some questions: Is the "dream project" doable in JavaScript? Or is C++ just the best option because it does not take as long to be interpreted at run time like JavaScript? What are the limitations? I can think of some: Need of a Powerful server depending on how much information the server has to process. Internet Speed; Sending the data of the Voxel positions to every player could add up being very high! The browser FPS might go down quickly if rendering to many objects. One way of fixing reducing the packages Could be to let the browser calculate some of the Voxel positions from Several Values. But that would slow down the Client side too. What about the more achievable project? I am almost 100% convinced that this is possible in JavaScript, and that there are several ways of doing this. This is just XY position Updating for now.. Hope this did make some sense. Please comment if you got something to say :D

    Read the article

  • Premature-Optimization and Performance Anxiety

    - by James Michael Hare
    While writing my post analyzing the new .NET 4 ConcurrentDictionary class (here), I fell into one of the classic blunders that I myself always love to warn about.  After analyzing the differences of time between a Dictionary with locking versus the new ConcurrentDictionary class, I noted that the ConcurrentDictionary was faster with read-heavy multi-threaded operations.  Then, I made the classic blunder of thinking that because the original Dictionary with locking was faster for those write-heavy uses, it was the best choice for those types of tasks.  In short, I fell into the premature-optimization anti-pattern. Basically, the premature-optimization anti-pattern is when a developer is coding very early for a perceived (whether rightly-or-wrongly) performance gain and sacrificing good design and maintainability in the process.  At best, the performance gains are usually negligible and at worst, can either negatively impact performance, or can degrade maintainability so much that time to market suffers or the code becomes very fragile due to the complexity. Keep in mind the distinction above.  I'm not talking about valid performance decisions.  There are decisions one should make when designing and writing an application that are valid performance decisions.  Examples of this are knowing the best data structures for a given situation (Dictionary versus List, for example) and choosing performance algorithms (linear search vs. binary search).  But these in my mind are macro optimizations.  The error is not in deciding to use a better data structure or algorithm, the anti-pattern as stated above is when you attempt to over-optimize early on in such a way that it sacrifices maintainability. In my case, I was actually considering trading the safety and maintainability gains of the ConcurrentDictionary (no locking required) for a slight performance gain by using the Dictionary with locking.  This would have been a mistake as I would be trading maintainability (ConcurrentDictionary requires no locking which helps readability) and safety (ConcurrentDictionary is safe for iteration even while being modified and you don't risk the developer locking incorrectly) -- and I fell for it even when I knew to watch out for it.  I think in my case, and it may be true for others as well, a large part of it was due to the time I was trained as a developer.  I began college in in the 90s when C and C++ was king and hardware speed and memory were still relatively priceless commodities and not to be squandered.  In those days, using a long instead of a short could waste precious resources, and as such, we were taught to try to minimize space and favor performance.  This is why in many cases such early code-bases were very hard to maintain.  I don't know how many times I heard back then to avoid too many function calls because of the overhead -- and in fact just last year I heard a new hire in the company where I work declare that she didn't want to refactor a long method because of function call overhead.  Now back then, that may have been a valid concern, but with today's modern hardware even if you're calling a trivial method in an extremely tight loop (which chances are the JIT compiler would optimize anyway) the results of removing method calls to speed up performance are negligible for the great majority of applications.  Now, obviously, there are those coding applications where speed is absolutely king (for example drivers, computer games, operating systems) where such sacrifices may be made.  But I would strongly advice against such optimization because of it's cost.  Many folks that are performing an optimization think it's always a win-win.  That they're simply adding speed to the application, what could possibly be wrong with that?  What they don't realize is the cost of their choice.  For every piece of straight-forward code that you obfuscate with performance enhancements, you risk the introduction of bugs in the long term technical debt of the application.  It will become so fragile over time that maintenance will become a nightmare.  I've seen such applications in places I have worked.  There are times I've seen applications where the designer was so obsessed with performance that they even designed their own memory management system for their application to try to squeeze out every ounce of performance.  Unfortunately, the application stability often suffers as a result and it is very difficult for anyone other than the original designer to maintain. I've even seen this recently where I heard a C++ developer bemoaning that in VS2010 the iterators are about twice as slow as they used to be because Microsoft added range checking (probably as part of the 0x standard implementation).  To me this was almost a joke.  Twice as slow sounds bad, but it almost never as bad as you think -- especially if you're gaining safety.  The only time twice is really that much slower is when once was too slow to begin with.  Think about it.  2 minutes is slow as a response time because 1 minute is slow.  But if an iterator takes 1 microsecond to move one position and a new, safer iterator takes 2 microseconds, this is trivial!  The only way you'd ever really notice this would be in iterating a collection just for the sake of iterating (i.e. no other operations).  To my mind, the added safety makes the extra time worth it. Always favor safety and maintainability when you can.  I know it can be a hard habit to break, especially if you started out your career early or in a language such as C where they are very performance conscious.  But in reality, these type of micro-optimizations only end up hurting you in the long run. Remember the two laws of optimization.  I'm not sure where I first heard these, but they are so true: For beginners: Do not optimize. For experts: Do not optimize yet. This is so true.  If you're a beginner, resist the urge to optimize at all costs.  And if you are an expert, delay that decision.  As long as you have chosen the right data structures and algorithms for your task, your performance will probably be more than sufficient.  Chances are it will be network, database, or disk hits that will be your slow-down, not your code.  As they say, 98% of your code's bottleneck is in 2% of your code so premature-optimization may add maintenance and safety debt that won't have any measurable impact.  Instead, code for maintainability and safety, and then, and only then, when you find a true bottleneck, then you should go back and optimize further.

    Read the article

  • My Package Version Number Appears Greater Yet apt-get Doesn't Select It

    - by nutznboltz
    Backstory: It was determined that when using lxc container VMs the Nagios nrpe shutdown script when run on the host of the containers would kill the nrpe processes inside the containers. This was remediated by changing the script to use pidfiles instead of searching the process table for the nrpe process. Regrettably start-stop-daemon is a C program that resulted from translating a Perl script and it shows. There are far too many global varibles in start-stop-daemon.c and although there are some nice blocks of comments there are far to few comments that explain the intent behind variable names such as "schedule" (the string "schedule" appears in many contexts.) The manual page for start-stop-daemon strongly suggests that unless you use the "--retry" option the start-stop-daemon program may return before the process it sent a signal to actually calls exit() and terminates, however it doesn't actually state this in plain English. The obtuseness of start-stop-daemon is most likely the reason that the "fixed" version of the script includes a dubious comment indicating that sometimes the pid file has not been removed. I can easily see why someone would not understand that he left the --retry option missing. This bug also causes failures when the script is given the "restart" option; the nrpe daemon will shutdown but not start up again. Did I mention that since applying the update our nrpe servers started crashing over and over? Repairing this is why I am doing this work. I have been working on remediating the fix. You can see my current work in this PPA. Actual Question: The upstream version number of nagios-nrpe-server in lucid-updates is 2.12-4ubuntu1.10.04.1 My PPA uses this version number 2.12-4ubuntu1.10.04.1.1~ppa1~lucid1 I check the rules here and use this test program and I am lead to believe that the version number I use in my PPA is greater than the one in lucid-updates yet when I ran: sudo add-apt-repository ppa:nutznboltz/nrpe-unbreak-lp-600941 sudo apt-get update sudo aptitiude dist-upgrade The replacement package was not installed. I was able to install it using sudo aptitude install nagios-nrpe-server=2.12-4ubuntu1.10.04.1.1~ppa1~lucid1 Can anyone explain this behavior? Why didn't my version number appear greater to "aptitude dist-upgrade"? Thanks $ cat /etc/apt/preferences Package: * Pin: release a=lucid-backports Pin-Priority: 400 Package: * Pin: release a=lucid-security Pin-Priority: 990 Package: * Pin: release a=lucid-updates Pin-Priority: 900 Package: * Pin: release a=lucid-proposed Pin-Priority: 400 $ ls /etc/apt/preferences.d/ $ Should not make any difference as a PPA cannot be in any of those pockets. I went ahead and bumped the version number in the PPA to 2.12-4ubuntu1.10.04.2~ppa1~lucid1. I'll see if that makes a difference. I do notice that lintian complains: W: nagios-nrpe-server: debian-revision-not-well-formed 2.12-4ubuntu1.10.04.2~ppa1~lucid1

    Read the article

  • ETPM Environment Health Monitoring Tools

    - by Paula Speranza-Hadley
    This post is to provide some useful information about the tools typically used by Oracle ETPM implementations for performance tuning and analysis.   This includes tools to monitor and gather performance information and statistics on the Database, Application Server, and Client (browser).  Enterprise Monitoring Tools Oracle Enterprise Manager - OEM Grid Control comes with a comprehensive set of performance and health metrics that allow monitoring of key components in your environment such as applications, application servers, databases, as well as the back-end components on which they rely, such as hosts, operating systems and storage. Tools for the Database Oracle Diagnostics Pack Automatic Workload Repository (AWR)  - this tool gets statistics from memory abut the Time Model or DB Time, Wait Events, Active Session History and High Load SWL queries Automatic Database Diagnostic Monitor (ADDM) - This self-diagnostic software is built into the database.  It examines and analyzes data captured in AWR to dertermine possible performance issues.  It locates the root cause of the issue, provides recommendations for correcting the issues and qualifies the expected benefit. Oracle Database Tuning Pack SQL Tuning Advisor - This enables you to submit one or more SQL statements as input and receive output in the form of specific advice or recommendations on how to tune statements.  The recommendation relates to collection of statistics on objects, creation on new indexes and restructuring of SQL statements. SQL Access Advisor - This enables you to optimize data access paths of SQL queries by recommending a proper set of materialized views, indexes and partitions for a given SQL workload. Tools for the Application Server Weblogic Console - is a web-based, user interface used to configure and control a set of WebLogic servers or clusters (i.e. a "domain").  In any logical group of WebLogic servers there must exist one admin server, which hosts the WebLogic Admin console application and manages the associated configuratoin files. WebLogic Administrators will use the Administration Console for a number of tasks, including: Starting and stopping WebLogic servers or entire clusters. Configuring server parameters, security, database connections and deployed applications. Viewing server status, health and metrics. Yourkit for Profiling - helps analyze synchronization issues, including: Which threads were calling wait(), and for how long Which threads were blocked on attempt to acquire a monitor held by another thread (synchronized methods/blocks), and for how long Tools for the Client Fiddler - allows you to inspect traffic logs, debug and set breakpoints. Firebug – allows you to inspect and edit HTML, monitor network activity and debug JavaScript

    Read the article

  • C# Performance Pitfall – Interop Scenarios Change the Rules

    - by Reed
    C# and .NET, overall, really do have fantastic performance in my opinion.  That being said, the performance characteristics dramatically differ from native programming, and take some relearning if you’re used to doing performance optimization in most other languages, especially C, C++, and similar.  However, there are times when revisiting tricks learned in native code play a critical role in performance optimization in C#. I recently ran across a nasty scenario that illustrated to me how dangerous following any fixed rules for optimization can be… The rules in C# when optimizing code are very different than C or C++.  Often, they’re exactly backwards.  For example, in C and C++, lifting a variable out of loops in order to avoid memory allocations often can have huge advantages.  If some function within a call graph is allocating memory dynamically, and that gets called in a loop, it can dramatically slow down a routine. This can be a tricky bottleneck to track down, even with a profiler.  Looking at the memory allocation graph is usually the key for spotting this routine, as it’s often “hidden” deep in call graph.  For example, while optimizing some of my scientific routines, I ran into a situation where I had a loop similar to: for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i]); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This loop was at a fairly high level in the call graph, and often could take many hours to complete, depending on the input data.  As such, any performance optimization we could achieve would be greatly appreciated by our users. After a fair bit of profiling, I noticed that a couple of function calls down the call graph (inside of ProcessElement), there was some code that effectively was doing: // Allocate some data required DataStructure* data = new DataStructure(num); // Call into a subroutine that passed around and manipulated this data highly CallSubroutine(data); // Read and use some values from here double values = data->Foo; // Cleanup delete data; // ... return bar; Normally, if “DataStructure” was a simple data type, I could just allocate it on the stack.  However, it’s constructor, internally, allocated it’s own memory using new, so this wouldn’t eliminate the problem.  In this case, however, I could change the call signatures to allow the pointer to the data structure to be passed into ProcessElement and through the call graph, allowing the inner routine to reuse the same “data” memory instead of allocating.  At the highest level, my code effectively changed to something like: DataStructure* data = new DataStructure(numberToProcess); for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i], data); } delete data; Granted, this dramatically reduced the maintainability of the code, so it wasn’t something I wanted to do unless there was a significant benefit.  In this case, after profiling the new version, I found that it increased the overall performance dramatically – my main test case went from 35 minutes runtime down to 21 minutes.  This was such a significant improvement, I felt it was worth the reduction in maintainability. In C and C++, it’s generally a good idea (for performance) to: Reduce the number of memory allocations as much as possible, Use fewer, larger memory allocations instead of many smaller ones, and Allocate as high up the call stack as possible, and reuse memory I’ve seen many people try to make similar optimizations in C# code.  For good or bad, this is typically not a good idea.  The garbage collector in .NET completely changes the rules here. In C#, reallocating memory in a loop is not always a bad idea.  In this scenario, for example, I may have been much better off leaving the original code alone.  The reason for this is the garbage collector.  The GC in .NET is incredibly effective, and leaving the allocation deep inside the call stack has some huge advantages.  First and foremost, it tends to make the code more maintainable – passing around object references tends to couple the methods together more than necessary, and overall increase the complexity of the code.  This is something that should be avoided unless there is a significant reason.  Second, (unlike C and C++) memory allocation of a single object in C# is normally cheap and fast.  Finally, and most critically, there is a large advantage to having short lived objects.  If you lift a variable out of the loop and reuse the memory, its much more likely that object will get promoted to Gen1 (or worse, Gen2).  This can cause expensive compaction operations to be required, and also lead to (at least temporary) memory fragmentation as well as more costly collections later. As such, I’ve found that it’s often (though not always) faster to leave memory allocations where you’d naturally place them – deep inside of the call graph, inside of the loops.  This causes the objects to stay very short lived, which in turn increases the efficiency of the garbage collector, and can dramatically improve the overall performance of the routine as a whole. In C#, I tend to: Keep variable declarations in the tightest scope possible Declare and allocate objects at usage While this tends to cause some of the same goals (reducing unnecessary allocations, etc), the goal here is a bit different – it’s about keeping the objects rooted for as little time as possible in order to (attempt) to keep them completely in Gen0, or worst case, Gen1.  It also has the huge advantage of keeping the code very maintainable – objects are used and “released” as soon as possible, which keeps the code very clean.  It does, however, often have the side effect of causing more allocations to occur, but keeping the objects rooted for a much shorter time. Now – nowhere here am I suggesting that these rules are hard, fast rules that are always true.  That being said, my time spent optimizing over the years encourages me to naturally write code that follows the above guidelines, then profile and adjust as necessary.  In my current project, however, I ran across one of those nasty little pitfalls that’s something to keep in mind – interop changes the rules. In this case, I was dealing with an API that, internally, used some COM objects.  In this case, these COM objects were leading to native allocations (most likely C++) occurring in a loop deep in my call graph.  Even though I was writing nice, clean managed code, the normal managed code rules for performance no longer apply.  After profiling to find the bottleneck in my code, I realized that my inner loop, a innocuous looking block of C# code, was effectively causing a set of native memory allocations in every iteration.  This required going back to a “native programming” mindset for optimization.  Lifting these variables and reusing them took a 1:10 routine down to 0:20 – again, a very worthwhile improvement. Overall, the lessons here are: Always profile if you suspect a performance problem – don’t assume any rule is correct, or any code is efficient just because it looks like it should be Remember to check memory allocations when profiling, not just CPU cycles Interop scenarios often cause managed code to act very differently than “normal” managed code. Native code can be hidden very cleverly inside of managed wrappers

    Read the article

  • Programming Windows 8 Apps with HTML, CSS, and JavaScript - All you need in one title

    It took me a while to work through the 800+ pages of this title. And yes, I really mean working not reading... Since the release of Windows 8 it should be obvious to any Windows software developer that there are new ways to develop, deploy and market applications for a broader audience. Interestingly, Microsoft started to narrow the technological gap between the various platforms - desktop, web, smartphone and XBox - and development of modern apps with HTML, CSS and JavaScript couldn't be easier. Kraig covers all facets of modern Windows 8 apps from the basic building blocks and project templates in Visual Studio 2012 over to the thoughtful use of specific APIs to finally proper deployment in the App Store and potential monetization. The organisation of the book is lied out like step by step instructions or a tutorial. Kraig literally takes the reader by the hand and explains in detail in his examples about the reasons, the pros, and the cons of a certain way of implementation. Thanks to cross-references to other chapters he leaves the choice to the reader to dig deeper right now or to catch up at some time later. Personally, I have to admit that I really enjoyed the relaxed writing style. App development is not dust-dry rocket science and it should be joyful to learn about new technologies. And thanks to the richness of the various chapters and samples you could easily adapt and transfer the knowledge gained in this title to other platforms like Windows Phone 8. And last but not least: The ebook is freely available at Amazon, Microsoft Press and O'Reilly. Don't think about it, just get the book. Now. Update: I already mentioned this title in other blog entries which are related to Microsoft certification. Feel free to read on and to discover more online resources: Learning content for MCSDs: Web Applications and Windows Store Apps using HTML5 More content for MCSDs: Web Applications and Windows Store Apps using HTML5 O'Reilly offers free webcasts on their site, too. And in case that you would like to know more about Kraig's book and his experience with various development teams, please checkout this one: Zero to App in Two Weeks: Programming Windows 8 Apps in HTML, CSS, and JavaScript. The recording should be available soon.

    Read the article

  • grub problem after grub-repair

    - by alireza
    I had two OS,win 7 and Ubuntu, I was working with win and went out of the room and when came back I saw Grub Rescue!!! I booted live and did grub_repaire and it still says multiple active partitions.operating system not found I feel that it can not find the ubuntu hard drive at all! ! ubuntu@ubuntu:/dev$ sudo fdisk -l Disk /dev/sda: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xde771741 Device Boot Start End Blocks Id System /dev/sda1 * 61 61 0 0 Empty /dev/sda2 2048 30146559 15072256 27 Hidden NTFS WinRE /dev/sda3 * 30146560 30351359 102400 7 HPFS/NTFS/exFAT /dev/sda4 30351360 334483299 152065970 7 HPFS/NTFS/exFAT ubuntu@ubuntu:/dev$ ls autofs dvdrw loop4 ppp ram5 shm tty15 tty29 tty42 tty56 ttyS10 ttyS24 uinput vcsa1 block ecryptfs loop5 psaux ram6 snapshot tty16 tty3 tty43 tty57 ttyS11 ttyS25 urandom vcsa2 bsg fb0 loop6 ptmx ram7 snd tty17 tty30 tty44 tty58 ttyS12 ttyS26 usbmon0 vcsa3 btrfs-control fd loop7 pts ram8 sr0 tty18 tty31 tty45 tty59 ttyS13 ttyS27 usbmon1 vcsa4 bus full loop-control ram0 ram9 stderr tty19 tty32 tty46 tty6 ttyS14 ttyS28 usbmon2 vcsa5 cdrom fuse mapper ram1 random stdin tty2 tty33 tty47 tty60 ttyS15 ttyS29 v4l vcsa6 cdrw fw0 mcelog ram10 rfkill stdout tty20 tty34 tty48 tty61 ttyS16 ttyS3 vcs vcsa7 char hpet mei ram11 rtc tty tty21 tty35 tty49 tty62 ttyS17 ttyS30 vcs1 vga_arbiter console input mem ram12 rtc0 tty0 tty22 tty36 tty5 tty63 ttyS18 ttyS31 vcs2 video0 core kmsg net ram13 sda tty1 tty23 tty37 tty50 tty7 ttyS19 ttyS4 vcs3 zero cpu log network_latency ram14 sda2 tty10 tty24 tty38 tty51 tty8 ttyS2 ttyS5 vcs4 cpu_dma_latency loop0 network_throughput ram15 sda3 tty11 tty25 tty39 tty52 tty9 ttyS20 ttyS6 vcs5 disk loop1 null ram2 sda4 tty12 tty26 tty4 tty53 ttyprintk ttyS21 ttyS7 vcs6 dri loop2 oldmem ram3 sg0 tty13 tty27 tty40 tty54 ttyS0 ttyS22 ttyS8 vcs7 dvd loop3 port ram4 sg1 tty14 tty28 tty41 tty55 ttyS1 ttyS23 ttyS9 vcsa ubuntu@ubuntu:/dev$ someone said { Remove the boot flag from sda1, by typing in a terminal: sudo fdisk /dev/sda1 Then press the 'a' key, and 'Enter'. Then press the '1' key, and 'Enter'. Then press the 'w' key, and 'Enter'. } but after grub-repair I got this log: http://paste.ubuntu.com/1371297/ then I try sudo fdisk /dev/sda1 and But It says unable to open /dev/sda1! which is right as sda1 is not in dev folder (look at the picture!) Can anybody help me? I need to work on my windows for the rest of the semester and don't care of my ubuntu. thank you

    Read the article

  • USB drives not recognized all of a sudden (usb_storage not loaded lsmod does not report usb_storage)

    - by Siddharth
    I have tried most of the advice on askubuntu and other sites, usb_storage enable to fdisk -l. But I am unable to find steps to get it working again. sudo lsusb results Bus.... skipped 4 lines Bus 004 Device 002: ID 413c:3012 Dell Computer Corp. Optical Wheel Mouse Bus 005 Device 002: ID 413c:2105 Dell Computer Corp. Model L100 Keyboard Bus 001 Device 005: ID 8564:1000 sudo dmseg | tail reports [ 69.567948] usb 1-4: USB disconnect, device number 4 [ 74.084041] usb 1-6: new high-speed USB device number 5 using ehci_hcd [ 74.240484] Initializing USB Mass Storage driver... [ 74.256033] scsi5 : usb-storage 1-6:1.0 [ 74.256145] usbcore: registered new interface driver usb-storage [ 74.256147] USB Mass Storage support registered. [ 74.257290] usbcore: deregistering interface driver usb-storage fdisk -l reports Device Boot Start End Blocks Id System /dev/sda1 * 2048 972656639 486327296 83 Linux /dev/sda2 972658686 976771071 2056193 5 Extended /dev/sda5 972658688 976771071 2056192 82 Linux swap / Solaris I think I need steps to install and get usb_storage module working. Edit : I tried sudo modprobe -v usb-storage reports sudo modprobe -v usb-storage insmod /lib/modules/3.2.0-48-generic-pae/kernel/drivers/usb/storage/usb-storage.ko Edit : jsiddharth@siddharth-desktop:~$ sudo udevadm monitor --udev monitor will print the received events for: UDEV - the event which udev sends out after rule processing UDEV [4757.144372] add /module/usb_storage (module) UDEV [4757.146558] remove /module/usb_storage (module) UDEV [4757.148707] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6 (usb) UDEV [4757.149699] add /bus/usb/drivers/usb-storage (drivers) UDEV [4757.151214] remove /bus/usb/drivers/usb-storage (drivers) UDEV [4757.156873] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0 (usb) UDEV [4757.160903] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9 (scsi) UDEV [4757.164672] add /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9/scsi_host/host9 (scsi_host) UDEV [4757.165163] remove /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9/scsi_host/host9 (scsi_host) UDEV [4757.165440] remove /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9 (scsi) Narrowing down more : Seems like I need usb_storage to load as a module jsiddharth@siddharth-desktop:~$ lsmod | grep usb usbserial 37201 0 usbhid 41937 0 hid 77428 1 usbhid Still no usb driver mounted. Nor does a device show up in /dev. Any step by step process to debug and fix this will be really helpful.

    Read the article

  • Collision detection when pathfinding with pathnodes, UDK

    - by Dave Voyles
    I'm trying to create a class that allows my AIController to path find using pathnodes (NOT NavMeshes). It's doing a swell job of going from point to point in a set order (although I would like for it to be a random patrol at some point), but it gets caught up on collision from time to time. I.E. He'll walk the same set path, and when he runs into the blocks in the middle of the map he continues to rub against them until they finish, and continues on his merry way to the next path node. How can I prevent this from happening, or at least have him move from the wall if he does a trace and detects that it is there? It looks like I need to use MoveToward() instead of MoveTo(), as MoveToward allows the pawn to adjust its course during movement. I'm just not sure of how to use those paramters. Mougli has a decent tutorial on it[/URL], but I can't seem to get it to work correctly with my pathnode array. class PathfindingAIController extends UDKBot; var array Waypoints; var int _PathNode; //declare it at the start so you can use it throughout the script var int CloseEnough; simulated function PostBeginPlay() { local PathNode Current; super.PostBeginPlay(); //add the pathnodes to the array foreach WorldInfo.AllActors(class'Pathnode',Current) { Waypoints.AddItem( Current ); } } simulated function Tick(float DeltaTime) { local int Distance; local Rotator DesiredRotation; super.Tick(DeltaTime); if (Pawn != None) { // Smoothly rotate the pawn towards the focal point DesiredRotation = Rotator(GetFocalPoint() - Pawn.Location); Pawn.FaceRotation(RLerp(Pawn.Rotation, DesiredRotation, 3.125f * DeltaTime, true), DeltaTime); } Distance = VSize2D(Pawn.Location - Waypoints[_PathNode].Location); if (Distance <= CloseEnough) { _PathNode++; } if (_PathNode >= Waypoints.Length) { _PathNode = 0; } GoToState('Pathfinding'); } auto state Pathfinding { Begin: if (Waypoints[_PathNode] != None) // make sure there is a pathnode to move to { MoveTo(Waypoints[_PathNode].Location); //move to it `log("STATE: Pathfinding"); } } DefaultProperties { CloseEnough=400 bIsplayer = True }

    Read the article

  • SQL University: What and why of database refactoring

    - by Mladen Prajdic
    This is a post for a great idea called SQL University started by Jorge Segarra also famously known as SqlChicken on Twitter. It’s a collection of blog posts on different database related topics contributed by several smart people all over the world. So this week is mine and we’ll be talking about database testing and refactoring. In 3 posts we’ll cover: SQLU part 1 - What and why of database testing SQLU part 2 - What and why of database refactoring SQLU part 3 - Tools of the trade This is a second part of the series and in it we’ll take a look at what database refactoring is and why do it. Why refactor a database To know why refactor we first have to know what refactoring actually is. Code refactoring is a process where we change module internals in a way that does not change that module’s input/output behavior. For successful refactoring there is one crucial thing we absolutely must have: Tests. Automated unit tests are the only guarantee we have that we haven’t broken the input/output behavior before refactoring. If you haven’t go back ad read my post on the matter. Then start writing them. Next thing you need is a code module. Those are views, UDFs and stored procedures. By having direct table access we can kiss fast and sweet refactoring good bye. One more point to have a database abstraction layer. And no, ORM’s don’t fall into that category. But also know that refactoring is NOT adding new functionality to your code. Many have fallen into this trap. Don’t be one of them and resist the lure of the dark side. And it’s a strong lure. We developers in general love to add new stuff to our code, but hate fixing our own mistakes or changing existing code for no apparent reason. To be a good refactorer one needs discipline and focus. Now we know that refactoring is all about changing inner workings of existing code. This can be due to performance optimizations, changing internal code workflows or some other reason. This is a typical black box scenario to the outside world. If we upgrade the car engine it still has to drive on the road (preferably faster) and not fly (no matter how cool that would be). Also be aware that white box tests will break when we refactor. What to refactor in a database Refactoring databases doesn’t happen that often but when it does it can include a lot of stuff. Let us look at a few common cases. Adding or removing database schema objects Adding, removing or changing table columns in any way, adding constraints, keys, etc… All of these can be counted as internal changes not visible to the data consumer. But each of these carries a potential input/output behavior change. Dropping a column can result in views not working anymore or stored procedure logic crashing. Adding a unique constraint shows duplicated data that shouldn’t exist. Foreign keys break a truncate table command executed from an application that runs once a month. All these scenarios are very real and can happen. With the proper database abstraction layer fully covered with black box tests we can make sure something like that does not happen (hopefully at all). Changing physical structures Physical structures include heaps, indexes and partitions. We can pretty much add or remove those without changing the data returned by the database. But the performance can be affected. So here we use our performance tests. We do have them, right? Just by adding a single index we can achieve orders of magnitude performance improvement. Won’t that make users happy? But what if that index causes our write operations to crawl to a stop. again we have to test this. There are a lot of things to think about and have tests for. Without tests we can’t do successful refactoring! Fixing bad code We all have some bad code in our systems. We usually refer to that code as code smell as they violate good coding practices. Examples of such code smells are SQL injection, use of SELECT *, scalar UDFs or cursors, etc… Each of those is huge code smell and can result in major code changes. Take SELECT * from example. If we remove a column from a table the client using that SELECT * statement won’t have a clue about that until it runs. Then it will gracefully crash and burn. Not to mention the widely unknown SELECT * view refresh problem that Tomas LaRock (@SQLRockstar on Twitter) and Colin Stasiuk (@BenchmarkIT on Twitter) talk about in detail. Go read about it, it’s informative. Refactoring this includes replacing the * with column names and most likely change to application using the database. Breaking apart huge stored procedures Have you ever seen seen a stored procedure that was 2000 lines long? I have. It’s not pretty. It hurts the eyes and sucks the will to live the next 10 minutes. They are a maintenance nightmare and turn into things no one dares to touch. I’m willing to bet that 100% of time they don’t have a single test on them. Large stored procedures (and functions) are a clear sign that they contain business logic. General opinion on good database coding practices says that business logic has no business in the database. That’s the applications part. Refactoring such behemoths requires writing lots of edge case tests for the stored procedure input/output behavior and then start to refactor it. First we split the logic inside into smaller parts like new stored procedures and UDFs. Those then get called from the master stored procedure. Once we’ve successfully modularized the database code it’s best to transfer that logic into the applications consuming it. This only leaves the stored procedure with common data manipulation logic. Of course this isn’t always possible so having a plethora of performance and behavior unit tests is absolutely necessary to confirm we’ve actually improved the codebase in some way.   Refactoring is not a popular chore amongst developers or managers. The former don’t like fixing old code, the latter can’t see the financial benefit. Remember how we talked about being lousy at estimating future costs in the previous post? But there comes a time when it must be done. Hopefully I’ve given you some ideas how to get started. In the last post of the series we’ll take a look at the tools to use and an example of testing and refactoring.

    Read the article

  • Did I lost my RAID again?

    - by BarsMonster
    Hi! A little history: 2 years ago I was really excited to find out that mdadm is so powerful so it even can reshape arrays so you can start with a smaller array and the grow it as you need. I've bought 3x1Tb drives and made RAID-5. It was fine for a year. Then I bought 2x more, and tried to reshape to RAID-6 out of 5 drives, and due to some mess with superblock versions, lost all content. Had to rebuild it from scratch, but 2Tb of data were gone. Yesterday I bought 2 more drives, and this time I had everything: properly built array, UPS. I've disabled write intent map, added 2 new drives as a spare and run a command to grow array to 7-disk. It started working, but speed was ridiculously slow, ~100kb/sec. AFter processing first 37Mb at such an amasing speed, one of old HDDs fails. I properly shutdown PC and disconnected failed drive. After bootup it appeared it recreated intent map as it was still in mdadm config, so I removed it from config and rebooted again. Now all I see is that all mdadm processes deadlocks, and don't do anything. PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1937 root 20 0 12992 608 444 D 0 0.1 0:00.00 mdadm 2283 root 20 0 12992 852 704 D 0 0.1 0:00.01 mdadm 2287 root 20 0 0 0 0 D 0 0.0 0:00.01 md0_reshape 2288 root 18 -2 12992 820 676 D 0 0.1 0:00.01 mdadm And all I see in mdstat is: $ cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid6 sdb1[1] sdg1[4] sdf1[7] sde1[6] sdd1[0] sdc1[5] 2929683456 blocks super 1.2 level 6, 1024k chunk, algorithm 2 [7/6] [UU_UUUU] [>....................] reshape = 0.0% (37888/976561152) finish=567604147.2min speed=0K/sec I've already tried mdadm 2.6.7, 3.1.4 and 3.2 - nothing helps. Did I lost my data again? Any suggestions how can I make it work? OS is Ubuntu Server 10.04.2... PS. Needless to say that data is unaccessible - I cannot mount /dev/md0 as save the most valuable data. You can see my disappointment - the very specific thing I was excited about failed twice taking 5Tb of my data with it.

    Read the article

  • Drawing multiple Textures as tilemap

    - by DocJones
    I am trying to draw a 2d game map and the objects on the map in a single pass. Here is my OpenGL initialization code // Turn off unnecessary operations glDisable(GL_DEPTH_TEST); glDisable(GL_LIGHTING); glDisable(GL_CULL_FACE); glDisable(GL_STENCIL_TEST); glDisable(GL_DITHER); glEnable(GL_BLEND); glEnable(GL_TEXTURE_2D); // activate pointer to vertex & texture array glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); My drawing code is being called by a NSTimer every 1/60 s. Here is the drawing code of my world object: - (void) draw:(NSRect)rect withTimedDelta:(double)d { GLint *t; glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, [_textureManager textureByName:@"blocks"]); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); for (int x=0; x<[_map getWidth] ; x++) { for (int y=0; y<[_map getHeight] ; y++) { GLint v[] = { 16*x ,16*y, 16*x+16,16*y, 16*x+16,16*y+16, 16*x ,16*y+16 }; t=[_textureManager getBlockWithNumber:[_map getBlockAtX:x andY:y]]; glVertexPointer(2, GL_INT, 0, v); glTexCoordPointer(2, GL_INT, 0, t); glDrawArrays(GL_QUADS, 0, 4); } } } (_textureManager is a Singelton only loading a texture once!) The object drawing codes is identical (except the nested loops) in terms of OpenGL calls: - (void) drawWithTimedDelta:(double)d { GLint *t; GLint v[] = { 16*xpos ,16*ypos, 16*xpos+16,16*ypos, 16*xpos+16,16*ypos+16, 16*xpos ,16*ypos+16 }; glBindTexture(GL_TEXTURE_2D, [_textureManager textureByName:_textureName]); t=[_textureManager getBlockWithNumber:12]; glVertexPointer(2, GL_INT, 0, v); glTexCoordPointer(2, GL_INT, 0, t); glDrawArrays(GL_QUADS, 0, 4); } As soon as my central drawing routine calls the two drawing methods the second call overlays the first one. i would expect the call to world.draw to draw the map and "stamp" the objects upon it. Debugging shows me, that the first call is performed correctly (world is being drawn), but the following call to all objects ONLY draws the objects, the rest of the scene is getting black. I think i need to blend the drawn textures, but i cant seem to figure out how. Any help is appreciated. Thanks PS: Here is the github link to the project. It may not be in sync of my post here, but for some more in-depth analysis it may help.

    Read the article

  • New hidden parameters in Oracle 11.2

    - by Mike Dietrich
    We really welcome every external review of our slides. And also recommendations from customers visiting our workshops. So it happened to me more than a week ago that Marco Patzwahl, the owner of MuniqSoft GmbH, had a very lengthy train ride in Germany (as the engine drivers go on strike this week it could have become even worse) and nothing better to do then reviewing our slide set. And he had plenty of recommendations. Besides that he pointed us to something at least I was not aware of and added it to the slides: In patch set 11.2.0.2 a new behaviour for datafile write errors has been implemented. With this release ANY write error to a datafile will cause the instance to abort. Before 11.2.0.2 those errors usually led to an offline datafile if the database operates in archivelog mode (your production database do, don’t they?!) and the datafile does not belong to the SYSTEM tablespace. Internal discussion found this behaviour not up-to-date and alligned with RAC systems and modern storages. Therefore it has been changed and a new underscore parameter got introduced. _DATAFILE_WRITE_ERRORS_CRASH_INSTANCE=TRUE This is the default setting´and the new behaviour beginning with Oracle 11.2.0.2 If you would like to revert to the pre-11.2.0.2 behaviour you’ll have to set in your init.ora/spfile this parameter to false. But keep in mind that there’s a reason why this has been changed. You’ll find more info in MOS Note: 7691270.8 and this topic in the current version of the slides on slide 255. Thanks to Marco for the review!!   And then I received an email from Kurt Van Meerbeeck today. Kurt is pretty well known in the Oracle community. And he’s the owner of jDUL/DUDE, a database unloading tool which bypasses the Oracle database engine and access data direclty from the blocks. Kurt visited the upgrade workshop two weeks ago in Belgium and did highlight to me that since Oracle 11.2.0.1 even though you haven’t set neither SGA_TARGET nor MEMORY_TARGET the database might still do resize operations. Reason why this behaviour has been changed: Prevention of ORA-4031 errors. But on databases with extremly high loads this can cause trouble. Further information can be found in MOS Note:1269139.1 . And the parameter set to TRUE by default is called _MEMORY_IMM_MODE_WITHOUT_AUTOSGA=TRUE This can be found now in the slide set as well on slide number 240. And thanks to Kurt for this information!!

    Read the article

  • Getting away from a customized Magento 1.4 installation - Magento 1.6, OpenCart, or others?

    - by Phil
    I'm dealing with a Magento 1.4.0.0 Community Edition installation with various undocumented changes to the core (mostly integration with an ERP system), an outdated Sweet Tooth Points & Rewards module and some custom payment providers. It also doubles as a mediocre blogging/CMS system. It has one store each for 3 different languages, with about 40 product categories for a few hundred products. [rant] With no prior experience with any PHP e-commerce systems, I find it very difficult to work with. I attempted to install Magento 1.4.0.0 on my local WAMP dev machine, it installs fine, but the main page or search do not show any products no matter what I do in the backend admin panel. I don't know what's wrong with it, and whatever information I googled is either too old or too new from Magento 1.4. Later I'm given FTP access to the testing server, which neither my manager or I have permission to install XDebug on, as apparantly it runs on the same server as the production server (yikes). Trying to learn how Magento works is torture. I spent a week trying to add some fields into the Onepage Checkout before giving up and went to work on something else. The template system, just like the rest of Magento, is a bloated mishmash of overcomplicated directory structures, weird config xml files and EAV databases. I went into 6 different models and several content blocks in the backend just to change what the front page looks like. With little-to-none helpful and clear documentation (unlike CodeIgniter) and various breaking changes between minor point revisions which makes it hard to find useful information, Magento 1.4 is a developer killer. [/rant] The client is planning to redesign the site and has decided it might as well as move on from this unsustainable, hacky, upgrade-unfriendly, developer-unfriendly mess. Magento 1.4 is starting to show its age, with Magento 1.7 coming soon, the client is considering upgrading to Magento 1.6 or 1.7 if it has improved from 1.4. The customizations done to the current Magento 1.4 installation will have to be redone, and a new license for the Sweet Tooth Points & Rewards module will have to be bought. The client is also open to other e-commerce systems. I've looked at OpenCart and it seems to be quite developer friendly with a fairly simple structure. I found some complaints regarding its performance when the shop has thousands of categories or products, but this is not an issue with the current number of products my client has. It seems to be solid ground for easy customization to bring the rewards system and ERP integration over. What should the client upgrade to in this case?

    Read the article

  • 25 Secrets for Faster ASP.NET: the Eagle has landed!

    - by Michaela Murray
    On Friday we launched our new free eBook, 25 Secrets for Faster ASP.NET Applications! Heading for 1000 of you have picked it up already, but if you haven’t got your copy yet, you can grab it from http://www.red-gate.com/25secrets. It’s the follow up to the wildly successful 50 Ways to Avoid, Find and Fix ASP.NET Performance Issues, which we released back in January this year (you can download from www.red-gate.com/50ways). Once again, we collected tips from some of the smartest brains in the ASP.NET community, but this time around, we’ve covered the latest stuff in the .NET framework – async/await, Web API, and more. Houston, we have a winner… In my original blogpost, I offered a Microsoft Surface as a prize for the best tip. Now, after some serious deliberation, our judges have settled on a winner. By a unanimous verdict, the prize goes to… (wait for it!) … Jeffrey Richter, for this cheeky number, Tip #1 in the new book: Want to build scalable websites and services? Work asynchronously One of the secrets to producing scalable websites and services is to perform all your I/O operations asynchronously to avoid blocking threads. When your thread issues a synchronous I/O request, the Windows kernel blocks the thread. This causes the thread pool to create a new thread, which allocates a lot of memory and wastes precious CPU time. Calling xxxAsync method and using C#’s async/await keywords allows your thread to return to the thread pool so it can be used for other things. This reduces the resource consumption of your app, allowing it to use more memory and improving response time to your clients. Congratulations Jeffrey! Of course, I also owe a massive thank you to everyone who’s been involved in the book, especially all the authors. It’s a real treat to work with a developer community that’s so keen to collaborate and to share their hard-won nuggets of performance knowhow. If you haven’t read it yet, I can’t recommend it highly enough. You can get it for free at www.red-gate.com/25secrets The full backstory for both eBooks: https://www.simple-talk.com/blogs/2012/11/15/application-performance-the-best-of-the-web/ https://www.simple-talk.com/blogs/2012/11/27/application-performance-episode-2-announcing-the-judges/ https://www.simple-talk.com/blogs/2013/01/25/free-ebook-50-ways-to-avoid-find-and-fix-asp-net-performance-issues/ https://www.simple-talk.com/blogs/2013/03/22/50-ways-to-avoid-find-and-fix-asp-net-performance-issues-the-next-generation/

    Read the article

  • IIS 7.0 informational HTTP status codes

    - by Samir R. Bhogayta
    1xx - Informational These HTTP status codes indicate a provisional response. The client computer receives one or more 1xx responses before the client computer receives a regular response. IIS 7.0 uses the following informational HTTP status codes: 100 - Continue. 101 - Switching protocols. 2xx - Success These HTTP status codes indicate that the server successfully accepted the request. IIS 7.0 uses the following success HTTP status codes: 200 - OK. The client request has succeeded. 201 - Created. 202 - Accepted. 203 - Nonauthoritative information. 204 - No content. 205 - Reset content. 206 - Partial content. 3xx - Redirection These HTTP status codes indicate that the client browser must take more action to fulfill the request. For example, the client browser may have to request a different page on the server. Or, the client browser may have to repeat the request by using a proxy server. IIS 7.0 uses the following redirection HTTP status codes: 301 - Moved permanently. 302 - Object moved. 304 - Not modified. 307 - Temporary redirect. 4xx - Client error These HTTP status codes indicate that an error occurred and that the client browser appears to be at fault. For example, the client browser may have requested a page that does not exist. Or, the client browser may not have provided valid authentication information. IIS 7.0 uses the following client error HTTP status codes: 400 - Bad request. The request could not be understood by the server due to malformed syntax. The client should not repeat the request without modifications. IIS 7.0 defines the following HTTP status codes that indicate a more specific cause of a 400 error: 400.1 - Invalid Destination Header. 400.2 - Invalid Depth Header. 400.3 - Invalid If Header. 400.4 - Invalid Overwrite Header. 400.5 - Invalid Translate Header. 400.6 - Invalid Request Body. 400.7 - Invalid Content Length. 400.8 - Invalid Timeout. 400.9 - Invalid Lock Token. 401 - Access denied. IIS 7.0 defines several HTTP status codes that indicate a more specific cause of a 401 error. The following specific HTTP status codes are displayed in the client browser but are not displayed in the IIS log: 401.1 - Logon failed. 401.2 - Logon failed due to server configuration. 401.3 - Unauthorized due to ACL on resource. 401.4 - Authorization failed by filter. 401.5 - Authorization failed by ISAPI/CGI application. 403 - Forbidden. IIS 7.0 defines the following HTTP status codes that indicate a more specific cause of a 403 error: 403.1 - Execute access forbidden. 403.2 - Read access forbidden. 403.3 - Write access forbidden. 403.4 - SSL required. 403.5 - SSL 128 required. 403.6 - IP address rejected. 403.7 - Client certificate required. 403.8 - Site access denied. 403.9 - Forbidden: Too many clients are trying to connect to the Web server. 403.10 - Forbidden: Web server is configured to deny Execute access. 403.11 - Forbidden: Password has been changed. 403.12 - Mapper denied access. 403.13 - Client certificate revoked. 403.14 - Directory listing denied. 403.15 - Forbidden: Client access licenses have exceeded limits on the Web server. 403.16 - Client certificate is untrusted or invalid. 403.17 - Client certificate has expired or is not yet valid. 403.18 - Cannot execute requested URL in the current application pool. 403.19 - Cannot execute CGI applications for the client in this application pool. 403.20 - Forbidden: Passport logon failed. 403.21 - Forbidden: Source access denied. 403.22 - Forbidden: Infinite depth is denied. 404 - Not found. IIS 7.0 defines the following HTTP status codes that indicate a more specific cause of a 404 error: 404.0 - Not found. 404.1 - Site Not Found. 404.2 - ISAPI or CGI restriction. 404.3 - MIME type restriction. 404.4 - No handler configured. 404.5 - Denied by request filtering configuration. 404.6 - Verb denied. 404.7 - File extension denied. 404.8 - Hidden namespace. 404.9 - File attribute hidden. 404.10 - Request header too long. 404.11 - Request contains double escape sequence. 404.12 - Request contains high-bit characters. 404.13 - Content length too large. 404.14 - Request URL too long. 404.15 - Query string too long. 404.16 - DAV request sent to the static file handler. 404.17 - Dynamic content mapped to the static file handler via a wildcard MIME mapping. 404.18 - Querystring sequence denied. 404.19 - Denied by filtering rule. 405 - Method Not Allowed. 406 - Client browser does not accept the MIME type of the requested page. 408 - Request timed out. 412 - Precondition failed. 5xx - Server error These HTTP status codes indicate that the server cannot complete the request because the server encounters an error. IIS 7.0 uses the following server error HTTP status codes: 500 - Internal server error. IIS 7.0 defines the following HTTP status codes that indicate a more specific cause of a 500 error: 500.0 - Module or ISAPI error occurred. 500.11 - Application is shutting down on the Web server. 500.12 - Application is busy restarting on the Web server. 500.13 - Web server is too busy. 500.15 - Direct requests for Global.asax are not allowed. 500.19 - Configuration data is invalid. 500.21 - Module not recognized. 500.22 - An ASP.NET httpModules configuration does not apply in Managed Pipeline mode. 500.23 - An ASP.NET httpHandlers configuration does not apply in Managed Pipeline mode. 500.24 - An ASP.NET impersonation configuration does not apply in Managed Pipeline mode. 500.50 - A rewrite error occurred during RQ_BEGIN_REQUEST notification handling. A configuration or inbound rule execution error occurred. Note Here is where the distributed rules configuration is read for both inbound and outbound rules. 500.51 - A rewrite error occurred during GL_PRE_BEGIN_REQUEST notification handling. A global configuration or global rule execution error occurred. Note Here is where the global rules configuration is read. 500.52 - A rewrite error occurred during RQ_SEND_RESPONSE notification handling. An outbound rule execution occurred. 500.53 - A rewrite error occurred during RQ_RELEASE_REQUEST_STATE notification handling. An outbound rule execution error occurred. The rule is configured to be executed before the output user cache gets updated. 500.100 - Internal ASP error. 501 - Header values specify a configuration that is not implemented. 502 - Web server received an invalid response while acting as a gateway or proxy. IIS 7.0 defines the following HTTP status codes that indicate a more specific cause of a 502 error: 502.1 - CGI application timeout. 502.2 - Bad gateway. 503 - Service unavailable. IIS 7.0 defines the following HTTP status codes that indicate a more specific cause of a 503 error: 503.0 - Application pool unavailable. 503.2 - Concurrent request limit exceeded.

    Read the article

  • DRY and SRP

    - by Timothy Klenke
    Originally posted on: http://geekswithblogs.net/TimothyK/archive/2014/06/11/dry-and-srp.aspxKent Beck’s XP Simplicity Rules (aka Four Rules of Simple Design) are a prioritized list of rules that when applied to your code generally yield a great design.  As you’ll see from the above link the list has slightly evolved over time.  I find today they are usually listed as: All Tests Pass Don’t Repeat Yourself (DRY) Express Intent Minimalistic These are prioritized.  If your code doesn’t work (rule 1) then everything else is forfeit.  Go back to rule one and get the code working before worrying about anything else. Over the years the community have debated whether the priority of rules 2 and 3 should be reversed.  Some say a little duplication in the code is OK as long as it helps express intent.  I’ve debated it myself.  This recent post got me thinking about this again, hence this post.   I don’t think it is fair to compare “Expressing Intent” against “DRY”.  This is a comparison of apples to oranges.  “Expressing Intent” is a principal of code quality.  “Repeating Yourself” is a code smell.  A code smell is merely an indicator that there might be something wrong with the code.  It takes further investigation to determine if a violation of an underlying principal of code quality has actually occurred. For example “using nouns for method names”, “using verbs for property names”, or “using Booleans for parameters” are all code smells that indicate that code probably isn’t doing a good job at expressing intent.  They are usually very good indicators.  But what principle is the code smell of Duplication pointing to and how good of an indicator is it? Duplication in the code base is bad for a couple reasons.  If you need to make a change and that needs to be made in a number of locations it is difficult to know if you have caught all of them.  This can lead to bugs if/when one of those locations is overlooked.  By refactoring the code to remove all duplication there will be left with only one place to change, thereby eliminating this problem. With most projects the code becomes the single source of truth for a project.  If a production code base is inconsistent with a five year old requirements or design document the production code that people are currently living with is usually declared as the current reality (or truth).  Requirement or design documents at this age in a project life cycle are usually of little value. Although comparing production code to external documentation is usually straight forward, duplication within the code base muddles this declaration of truth.  When code is duplicated small discrepancies will creep in between the two copies over time.  The question then becomes which copy is correct?  As different factions debate how the software should work, trust in the software and the team behind it erodes. The code smell of Duplication points to a violation of the “Single Source of Truth” principle.  Let me define that as: A stakeholder’s requirement for a software change should never cause more than one class to change. Violation of the Single Source of Truth principle will always result in duplication in the code.  However, the inverse is not always true.  Duplication in the code does not necessarily indicate that there is a violation of the Single Source of Truth principle. To illustrate this, let’s look at a retail system where the system will (1) send a transaction to a bank and (2) print a receipt for the customer.  Although these are two separate features of the system, they are closely related.  The reason for printing the receipt is usually to provide an audit trail back to the bank transaction.  Both features use the same data:  amount charged, account number, transaction date, customer name, retail store name, and etcetera.  Because both features use much of the same data, there is likely to be a lot of duplication between them.  This duplication can be removed by making both features use the same data access layer. Then start coming the divergent requirements.  The receipt stakeholder wants a change so that the account number has the last few digits masked out to protect the customer’s privacy.  That can be solve with a small IF statement whilst still eliminating all duplication in the system.  Then the bank wants to take a picture of the customer as well as capture their signature and/or PIN number for enhanced security.  Then the receipt owner wants to pull data from a completely different system to report the customer’s loyalty program point total. After a while you realize that the two stakeholders have somewhat similar, but ultimately different responsibilities.  They have their own reasons for pulling the data access layer in different directions.  Then it dawns on you, the Single Responsibility Principle: There should never be more than one reason for a class to change. In this example we have two stakeholders giving two separate reasons for the data access class to change.  It is clear violation of the Single Responsibility Principle.  That’s a problem because it can often lead the project owner pitting the two stakeholders against each other in a vein attempt to get them to work out a mutual single source of truth.  But that doesn’t exist.  There are two completely valid truths that the developers need to support.  How is this to be supported and honour the Single Responsibility Principle?  The solution is to duplicate the data access layer and let each stakeholder control their own copy. The Single Source of Truth and Single Responsibility Principles are very closely related.  SST tells you when to remove duplication; SRP tells you when to introduce it.  They may seem to be fighting each other, but really they are not.  The key is to clearly identify the different responsibilities (or sources of truth) over a system.  Sometimes there is a single person with that responsibility, other times there are many.  This can be especially difficult if the same person has dual responsibilities.  They might not even realize they are wearing multiple hats. In my opinion Single Source of Truth should be listed as the second rule of simple design with Express Intent at number three.  Investigation of the DRY code smell should yield to the proper application SST, without violating SRP.  When necessary leave duplication in the system and let the class names express the different people that are responsible for controlling them.  Knowing all the people with responsibilities over a system is the higher priority because you’ll need to know this before you can express it.  Although it may be a code smell when there is duplication in the code, it does not necessarily mean that the coder has chosen to be expressive over DRY or that the code is bad.

    Read the article

  • GParted detects entire disk as UNALLOCATED SPACE + hd0 out of disk

    - by msPeachy
    Good day to everyone. I hope someone can help me with my problem. I have a dual boot Windows and Ubuntu system. I recently encountered an hd0 out of disk error and wasn't able to boot Ubuntu. So I booted into Windows. After 2 to 3 times of booting and rebooting Windows, I tried booting Ubuntu again but still I get the same hd0 out of disk error. I decided to run Ubuntu from LIVEUSB to try to fix my Ubuntu partition using GParted, but when I run GParted, it shows my entire disk as UNALLOCATED SPACE! The strange thing is that Nautilus still shows and mounts my partitions. Also every time I boot into Windows , my partitions exists and I am able to read and write to them. I have no idea what is wrong. Please help! I can't stand using Windows since most of the tools I use are in Ubuntu. I don't mind reinstalling Ubuntu. In fact I already tried reinstalling using the LIVEUSB but since GParted or the Ubuntu installer itself does not recognize my partitions and shows the entire disk as unallocated space, I decided not to continue. I am currently running Ubuntu from LIVEUSB. Here's the outpuf of sudo fdisk -l Disk /dev/sda: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xb30ab30a Device Boot Start End Blocks Id System /dev/sda1 * 2048 104869887 52433920 83 Linux /dev/sda2 104869888 105074687 102400 7 HPFS/NTFS/exFAT /dev/sda3 105074688 156149759 25537536 7 HPFS/NTFS/exFAT /dev/sda4 156151800 625153409 234500805 f W95 Ext'd (LBA) /dev/sda5 156151808 169156591 6502392 82 Linux swap / Solaris /dev/sda6 169158656 294991871 62916608 7 HPFS/NTFS/exFAT /dev/sda7 294993920 471037944 88022012+ 7 HPFS/NTFS/exFAT /dev/sda8 471041928 625121152 77039612+ 7 HPFS/NTFS/exFAT When I run, sudo parted -l, I got this error message: ubuntu@ubuntu:~$ sudo parted -l Error: Can't have a partition outside the disk! UPDATE I think I might know the problem. The total sectors of sda is 625142448 but the extended partition (sda4) ends at 625153409. Now, my question is, how do I fix this or modify the extended partition (sda4) to matched the total number of sectors? Anyone, please??? UPDATE I was able to fix the unallocated space issue with the help of Rod Smith's tool called fixparts I am now able to view my partitions via GParted in LiveUSB. But the error: hd0 out of disk. Press any key to continue... still persists on reboot. I still can't boot into Ubuntu. Can someone help me please???

    Read the article

  • Are IE 9 will have a place in heart of user ?

    - by anirudha
    in a advertisement of IE 9 MSFT compare two product first is their IE9 and second is chrome 6. I know 6 is not currently [9] but no objection because may be they make ads when 6 is currently version and have RC or beta in their hands. on IE 9 test-drive website they show many of people ads to show the user that IE9 is performance better or other chrome or Firefox not. well they not compare with Firefox because last days firefox not still in news and search trends like before RC release many of user googling for them. Well I myself found IE9 perform smoother then chrome. but what MSFT do after IE9 nothing they waiting for IE 10 not for give updates not as well as Google chrome and Firefox. Are IE9 have anything new for Developer even a small or big. well they tell you blah or useless things everytime when they make for next version no matter for you but a matter for them because they add a new thing even useless for developer. I am not have any feeling with IE bad but I like to make reviews as well as I can make. I show you something who I experience with IE and someother browser like Chrome and Firefox. IE 9 still have no plugin as well as other provided like Firefox have Firebug a great utilities who is best option for developer to debug their code. IE9 developer tool is good but still you never customize them or readymade customization available to work as in firefox many of person make customization for firebug like example :- firepicker for picking color in firebug , firebug autocomplete for intellisense like feature when you write JavaScript inside console panel , pixelperfect , firequery , sitepoint reference and many other great example we all love to use. as other things that Firefox give many things customizable like themes , ui and many thing customization means more thing user or developer want to make themselves and more contribution make them better software so Firefox is great because customization is a great thing inside firefox and chrome. if you read some post of developer on MSDN to what’s new in IE 9 developer tool that you feel they are joking whenever you see some other things of Firefox and chrome. in a Firefox a plugin perform many much things but in IE still use IE 9 developer tool no other option like in Firefox use Firebug and many other utilities to make development easier and time saving and best as we can do.if you see Firefox page on mozilla that sublines of firefox is high performance easy customization advanced security well you can say what’s performance but there is no comparison with IE because IE have only performance and nothing else. but Firefox have these three thing to make product love. and third thing I really love that security yeah security. from long time before whenever IE6 is no hackproff and many other easily hack IE6 whenever Firefox is secure. I found myself that many of website install a software on client’s computer and they still not know about them so they track everything. sometime they hijack the homepage and make their website as their homepage. sometime they do something and you trying  to go to  any website then they go to their site first. the problem I telling about not long before it’s time of late in 2008 whenever Firefox is much better then IE6. if someone have bad experience with anyone of these software share with us I like to hear your voice. whenever IE still not for use Firefox is a good option for us even user or developer. I not know why someone make next version of IE. IE still have time to go away from Web. Firefox not rude as IE they still believe in user feedback and chrome is also open the door for feedback on their product gooogle Chrome. but what thing they made in IE on user feedback nothing. they still thing to teach what they maked not thing about what user need. if you spent some hour on firefox and chrome then you found what’s matter. what thing you have whenever you use IE or other browser like google chrome and Firefox :- as a user IE give you nothing even tell you blah blah and more blah but still next version of IE means next IE6 for the web. as in Google chrome you find plugins addons or customization to make experience better but in IE9 you can’t customize anything even the themes they have by default. Firefox already have a great list of plugins or addons to make experience better with Web but IE9 have nothing. this means IE9 not for user and other like chrome and firefox give you much better experience then IE. next thing after user is developer. first thing is that all developer want smooth development who save their time not take too perhaps saving.posts on IE9 show that a list of thing improved in IE 9 developer tool but are one developer tool enough for web development so developer need more utilities to solve different different type of puzzle who IE 9 never give like in Firefox you have utilities to do a task even small or big one. in chrome same experience you have but IE9 never give any plugin or utilities to make our work faster even they are new headache for developer because IE not give update as soon as other because in Firefox and in chrome if a bug is reported then they solve them fast and distribute them in next version of software very soon but in IE wait for a long time like IE 9 and IE 8 have no official release between them as update. As my conclusion there is no reason to use IE and adopt 9 again. it’s really not for Developer or user even newbie or smart people. as a rule I want to beware you with IE because it’s my responsibilities to move the thing in good way as I can make. well are you sure that there is no reason or profit they thing to have with IE9  if not why they forget luna [windows xp] user. because they are old nothing they want to force user to give them some money by purchasing a new version of OS. so this a thing why they marketed their software. if you thing about what firefox and chrome want to make : Mozilla's mission is to promote openness, innovation and opportunity on the web. chrome mission we all see whenever we use them. but IE9 is a trick they promote because they want to add something to next version of windows. if somebody like IE9 [even surprised by ads they see or post they read] then they purchase windows soon as they possible. Well you feel that I am opposition of IE9 and favor of chrome and Firefox yeah you feel right I hate IE from a heart not from a pencil. well you get same thing when you have trying three product major I described here Chrome firefox and IE. well don’t believe on the blogs , posts or article who are provided by the merchant or vender’s website. open the eyes read and thing what they talk and feel are they really true. if you confused that compare with some other. now you know the true because no one telling so badly as a user can described who use them not only one who make their feature. always open the eyes don’t believe use your mind and find the truth. thanks for reading my post good bye and take care

    Read the article

  • How to Identify Which Hardware Component is Failing in Your Computer

    - by Chris Hoffman
    Concluding that your computer has a hardware problem is just the first step. If you’re dealing with a hardware issue and not a software issue, the next step is determining what hardware problem you’re actually dealing with. If you purchased a laptop or pre-built desktop PC and it’s still under warranty, you don’t need to care about this. Have the manufacturer fix the PC for you — figuring it out is their problem. If you’ve built your own PC or you want to fix a computer that’s out of warranty, this is something you’ll need to do on your own. Blue Screen 101: Search for the Error Message This may seem like obvious advice, but searching for information about a blue screen’s error message can help immensely. Most blue screens of death you’ll encounter on modern versions of Windows will likely be caused by hardware failures. The blue screen of death often displays information about the driver that crashed or the type of error it encountered. For example, let’s say you encounter a blue screen that identified “NV4_disp.dll” as the driver that caused the blue screen. A quick Google search will reveal that this is the driver for NVIDIA graphics cards, so you now have somewhere to start. It’s possible that your graphics card is failing if you encounter such an error message. Check Hard Drive SMART Status Hard drives have a built in S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) feature. The idea is that the hard drive monitors itself and will notice if it starts to fail, providing you with some advance notice before the drive fails completely. This isn’t perfect, so your hard drive may fail even if SMART says everything is okay. If you see any sort of “SMART error” message, your hard drive is failing. You can use SMART analysis tools to view the SMART health status information your hard drives are reporting. Test Your RAM RAM failure can result in a variety of problems. If the computer writes data to RAM and the RAM returns different data because it’s malfunctioning, you may see application crashes, blue screens, and file system corruption. To test your memory and see if it’s working properly, use Windows’ built-in Memory Diagnostic tool. The Memory Diagnostic tool will write data to every sector of your RAM and read it back afterwards, ensuring that all your RAM is working properly. Check Heat Levels How hot is is inside your computer? Overheating can rsult in blue screens, crashes, and abrupt shut downs. Your computer may be overheating because you’re in a very hot location, it’s ventilated poorly, a fan has stopped inside your computer, or it’s full of dust. Your computer monitors its own internal temperatures and you can access this information. It’s generally available in your computer’s BIOS, but you can also view it with system information utilities such as SpeedFan or Speccy. Check your computer’s recommended temperature level and ensure it’s within the appropriate range. If your computer is overheating, you may see problems only when you’re doing something demanding, such as playing a game that stresses your CPU and graphics card. Be sure to keep an eye on how hot your computer gets when it performs these demanding tasks, not only when it’s idle. Stress Test Your CPU You can use a utility like Prime95 to stress test your CPU. Such a utility will fore your computer’s CPU to perform calculations without allowing it to rest, working it hard and generating heat. If your CPU is becoming too hot, you’ll start to see errors or system crashes. Overclockers use Prime95 to stress test their overclock settings — if Prime95 experiences errors, they throttle back on their overclocks to ensure the CPU runs cooler and more stable. It’s a good way to check if your CPU is stable under load. Stress Test Your Graphics Card Your graphics card can also be stress tested. For example, if your graphics driver crashes while playing games, the games themselves crash, or you see odd graphical corruption, you can run a graphics benchmark utility like 3DMark. The benchmark will stress your graphics card and, if it’s overheating or failing under load, you’ll see graphical problems, crashes, or blue screens while running the benchmark. If the benchmark seems to work fine but you have issues playing a certain game, it may just be a problem with that game. Swap it Out Not every hardware problem is easy to diagnose. If you have a bad motherboard or power supply, their problems may only manifest through occasional odd issues with other components. It’s hard to tell if these components are causing problems unless you replace them completely. Ultimately, the best way to determine whether a component is faulty is to swap it out. For example, if you think your graphics card may be causing your computer to blue screen, pull the graphics card out of your computer and swap in a new graphics card. If everything is working well, it’s likely that your previous graphics card was bad. This isn’t easy for people who don’t have boxes of components sitting around, but it’s the ideal way to troubleshoot. Troubleshooting is all about trial and error, and swapping components out allows you to pin down which component is actually causing the problem through a process of elimination. This isn’t a complete guide to everything that could likely go wrong and how to identify it — someone could write a full textbook on identifying failing components and still not cover everything. But the tips above should give you some places to start dealing with the more common problems. Image Credit: Justin Marty on Flickr     

    Read the article

  • Ubuntu Install 11.10 doesn't recognize Windows 7 installation with new HDD

    - by arlendo
    Replaced my crashed HDD with a Seagate 2TB Sata (bought from a company who pulled it from a working computer, OS unknown) and did a fresh install of Windows 7. Windows shows 100MB boot partition (bootable NTFS) and 200GB Windows partition (NTFS), the rest is unallocated. Win7 Disk Management says the partitioning type is Master Boot Record. Win7 boots and runs fine. Ubuntu 11.10 Install procedes to Allocate Drive Space screen and should say This computer currently has Windows 7 on it. What would you like to do? Instead, it says something like Install doesn't detect any existing OS on this computer. When I click on Something else, the partition table shows only the unallocated space of 1.8TB. Ubuntu Disk Utility says Partitioning: Master Boot Record, but GParted Live says Partition Table: gpt. It was my original intention to have the Windows boot partition and application partition, then install Ubuntu 11.10 using boot, root, swap, and home partitions, and maybe another partition just for data (mostly photos). Currently, I would be happy if I could just get Ubuntu installed along with Win7. I am aware of the MBR limits of 3 Primary partitions and 1 Extended partition. I suspect that my new HDD is partitioned for GPT and that is why Ubuntu can't see the Win7 installation. Am I on the right track? I was going to use Windows Disk Management to convert GPT to MBR but I only have the one drive on my AMD-64 mini-computer and it says I have to empty the drive of all partitions before I can access the Convert command. And I can't find any bootable software that would allow me to do that conversion. Here is the result of sudo fdisk -l: ubuntu@ubuntu:~$ sudo fdisk -l WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted. Disk /dev/sda: 2000.4 GB, 2000398934016 bytes 224 heads, 19 sectors/track, 918004 cylinders, total 3907029168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xd4a68c18 Device Boot Start End Blocks Id System /dev/sda1 * 2048 206847 102400 7 HPFS/NTFS/exFAT /dev/sda2 206848 419637247 209715200 7 HPFS/NTFS/exFAT ubuntu@ubuntu:~$ Keep in mind that I'm a definite newbie to screwing around with the inner workings of Ubuntu. I previously had Ubuntu 10.04 running with Vista and I don't remember even having to partition anything that wasn't automatic in the install. Thanks for taking a look here. My Win7 is running fine but I miss my Ubuntu.

    Read the article

  • Code review recommendations and Code Smells

    - by Michael Freidgeim
    Some time ago Twitter told that I am similar to Boris Lipschitz . Indeed he is also .Net programmer from Russia living in Australia. I‘ve read his list of Code Review points and found them quite comprehensive. A few points  were not clear for me, and it forced me for a further reading.In particular the statement “Exception should not be used to return a status or an error code.” wasn’t fully clear for me, because sometimes we store an exception as an object with all error details and I believe it’s a valid approach. However I agree that throwing exceptions should be avoided, if you expect to return error as a part of a normal flow. Related link: http://codeutopia.net/blog/2010/03/11/should-a-failed-function-return-a-value-or-throw-an-exception/ Another point slightly puzzled me“If Thread.Sleep() is used, can it be replaced with something else, ei Timer, AutoResetEvent, etc” . I believe, that there are very rare cases, when anyone using Thread.Sleep in any production code. Usually it is used in mocks and prototypes.I had to look further to clarify “Dependency injection is used instead of Service Location pattern”.Even most of articles has some preferences to Dependency injection, there are also advantages to use Service Location. E.g see http://geekswithblogs.net/KyleBurns/archive/2012/04/27/dependency-injection-vs.-service-locator.aspx. http://www.cookcomputing.com/blog/archives/000587.html  refers to Concluding Thoughts of Martin Fowler The choice between Service Locator and Dependency Injection is less important than the principle of separating service configuration from the use of services within an applicationThe post had a link to excellent article Code Smells of Jeff Atwood, but the statement, that “code should not pass a review if it violates any of the  code smells” sound too strict for my environment. In particular, I disagree with “Dead Code” recommendation “Ruthlessly delete code that isn't being used. That's why we have source control systems!”. If there is a chance that not used code will be required in a future, it is convenient to keep it as commented or #if/#endif blocks with appropriate explanation, why it could be required in the future. TFS is a good source control system, but context search in source code of current solution is much easier than finding something in the previous versions of the code.I also found a link to a good book “Clean Code.A.Handbook.of.Agile.Software”

    Read the article

< Previous Page | 202 203 204 205 206 207 208 209 210 211 212 213  | Next Page >