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  • A list of 'best practices' for extending the life between charges of a notebook battery.

    - by Tim Visher
    Hello Everyone, I'd like to compile a list of best practices for getting the most out of a single charge of a typical notebook battery (be it Li-Ion or Li-Poly). Sources would be great as well. I've heard, for instance, that the best things to do to improve battery performance (not the total lifetime of the battery, just single charge performance) are, in descending order of effectiveness: Turn your display all the way down. Turn off WiFi Turn off Bluetooth Spin down disks when they're not in use. etc… I'd like to get sources together for these and other tips for extending life-between-charge for any battery on any notebook (as these really are all about Demand Management rather than Life lime extension. Thanks!

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  • Why does Snow Leopard report incorrect battery levels for Bluetooth input devices after switching them to Apple rechargeable batteries?

    - by GeneQ
    I have a Magic Trackpad, Magic Mouse and the Apple Wireless keyboard. They work fine. Two days ago, doing my part for the environment, I changed all their batteries to Apple rechargeable batteries. Today I noticed that the battery level meter for all three devices report the wrong battery level. The trackpad reports 93% charge, the keyboard 75% charge and the mouse 65% charge. This can't be right; these are fully charged new batteries. They can't possible drop that much within 48 hours. Has anyone else encountered this problem? And are there any solutions?

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  • To have a long life with the battery it has to be separated from the Laptop after each use

    - by laptopo1 dsad
    To have a long life with the battery it has to be separated from the Laptop after each use Developing a Laptop and concern about it's battery life Don't be concerned follow this advice how to deal with your Laptop battery. A fresh power supply of your Laptop can be purchased in a very low charge condition, and must be fully charged before use. A different battery pack needs to be fully charged and fully discharged or cycled as much as five times to condition them into performing at full capacity. And also refer your manual instructions of one's Laptop for charging instructions. Inspiron 15z battery Tips: Unplug battery after use: To have a long life with the battery it has to be separated from the Laptop after each use. Clean battery contacts often: Clean your battery's metal contacts once in a month with a cloth moistened with rubbing alcohol. This prevents the transfer of power out of your battery additional efficient. Turn off the WiFi and Bluetooth, in any other case being used: Usually, we activate our WiFi or Bluetooth for whatever reason and tend to forget to Off it, that could spark a huge relieve your battery, Shut off right after the usage. Dell XPS L501x battery Dim notebook screen: When you're with your Laptop in Daytime, you will need for full brightness. But also in case of Night, just dim the screen reducing brightness, which will consume more charge once the brightness might be more and also It's essential on your eyes to determine lesser brighten screen inside nights. Dell Inspiron 17R battery Have hardly any Background programs: Letting more programs to own behind the screen could consume more Dell Inspiron N4010 battery charge hence have very few without background programs are Better. Make use of the Hard disk drive more than CD/DVD drive: Making use of disc drive instead your CD/DVD drive could consume less battery power. Latitude E5400 Battery

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  • RPi and Java Embedded GPIO: Using Java to read input

    - by hinkmond
    Now that we've learned about using Java code to control the output of the Raspberry Pi GPIO ports (by lighting up LEDs from a Java app on the RPi for now and noting in the future the same Java code can be used to drive industrial automation or medical equipment, etc.), let's move on to learn about reading input from the RPi GPIO using Java code. As before, we need to start out with the necessary hardware. For this exercise we will connect a Static Electricity Detector to the RPi GPIO port and read the value of that sensor using Java code. The circuit we'll use is from William J. Beaty and is described at this Web link. See: Static Electricity Detector He calls it an "Electric Charge" detector, which is a bit misleading. A Field Effect Transistor is subject to nearby electro-magnetic fields, such as a static charge on a nearby object, not really an electric charge. So, this sensor will detect static electricity (or ghosts if you are into paranormal activity ). Take a look at the circuit and in the next blog posts we'll step through how to connect it to the GPIO port of your RPi and then how to write Java code to access this fun sensor. Hinkmond

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  • SSAS 2008 R2– Little Gems

    - by ACALVETT
    I have spent the last few days working with SSAS 2008 R2 and noticed a few small enhancements which many people probably won’t notice but i will list them here and why they are important to me. New profiler events Commit: This is a new sub class event for “progress report end”. This represents the elapsed time taken for the server to commit your data. It is important because for the duration of this event a server level lock will be in place blocking all incoming connections and causing time out...(read more)

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  • Developing web apps using ASP.NET MVC 3, Razor and EF Code First - Part 1

    - by shiju
    In this post, I will demonstrate web application development using ASP. NET MVC 3, Razor and EF code First. This post will also cover Dependency Injection using Unity 2.0 and generic Repository and Unit of Work for EF Code First. The following frameworks will be used for this step by step tutorial. ASP.NET MVC 3 EF Code First CTP 5 Unity 2.0 Define Domain Model Let’s create domain model for our simple web application Category class public class Category {     public int CategoryId { get; set; }     [Required(ErrorMessage = "Name Required")]     [StringLength(25, ErrorMessage = "Must be less than 25 characters")]     public string Name { get; set;}     public string Description { get; set; }     public virtual ICollection<Expense> Expenses { get; set; } }   Expense class public class Expense {             public int ExpenseId { get; set; }            public string  Transaction { get; set; }     public DateTime Date { get; set; }     public double Amount { get; set; }     public int CategoryId { get; set; }     public virtual Category Category { get; set; } } We have two domain entities - Category and Expense. A single category contains a list of expense transactions and every expense transaction should have a Category. In this post, we will be focusing on CRUD operations for the entity Category and will be working on the Expense entity with a View Model object in the later post. And the source code for this application will be refactored over time. The above entities are very simple POCO (Plain Old CLR Object) classes and the entity Category is decorated with validation attributes in the System.ComponentModel.DataAnnotations namespace. Now we want to use these entities for defining model objects for the Entity Framework 4. Using the Code First approach of Entity Framework, we can first define the entities by simply writing POCO classes without any coupling with any API or database library. This approach lets you focus on domain model which will enable Domain-Driven Development for applications. EF code first support is currently enabled with a separate API that is runs on top of the Entity Framework 4. EF Code First is reached CTP 5 when I am writing this article. Creating Context Class for Entity Framework We have created our domain model and let’s create a class in order to working with Entity Framework Code First. For this, you have to download EF Code First CTP 5 and add reference to the assembly EntitFramework.dll. You can also use NuGet to download add reference to EEF Code First.    public class MyFinanceContext : DbContext {     public MyFinanceContext() : base("MyFinance") { }     public DbSet<Category> Categories { get; set; }     public DbSet<Expense> Expenses { get; set; }         }   The above class MyFinanceContext is derived from DbContext that can connect your model classes to a database. The MyFinanceContext class is mapping our Category and Expense class into database tables Categories and Expenses using DbSet<TEntity> where TEntity is any POCO class. When we are running the application at first time, it will automatically create the database. EF code-first look for a connection string in web.config or app.config that has the same name as the dbcontext class. If it is not find any connection string with the convention, it will automatically create database in local SQL Express database by default and the name of the database will be same name as the dbcontext class. You can also define the name of database in constructor of the the dbcontext class. Unlike NHibernate, we don’t have to use any XML based mapping files or Fluent interface for mapping between our model and database. The model classes of Code First are working on the basis of conventions and we can also use a fluent API to refine our model. The convention for primary key is ‘Id’ or ‘<class name>Id’.  If primary key properties are detected with type ‘int’, ‘long’ or ‘short’, they will automatically registered as identity columns in the database by default. Primary key detection is not case sensitive. We can define our model classes with validation attributes in the System.ComponentModel.DataAnnotations namespace and it automatically enforces validation rules when a model object is updated or saved. Generic Repository for EF Code First We have created model classes and dbcontext class. Now we have to create generic repository pattern for data persistence with EF code first. If you don’t know about the repository pattern, checkout Martin Fowler’s article on Repository Let’s create a generic repository to working with DbContext and DbSet generics. public interface IRepository<T> where T : class     {         void Add(T entity);         void Delete(T entity);         T GetById(long Id);         IEnumerable<T> All();     }   RepositoryBasse – Generic Repository class public abstract class RepositoryBase<T> where T : class { private MyFinanceContext database; private readonly IDbSet<T> dbset; protected RepositoryBase(IDatabaseFactory databaseFactory) {     DatabaseFactory = databaseFactory;     dbset = Database.Set<T>(); }   protected IDatabaseFactory DatabaseFactory {     get; private set; }   protected MyFinanceContext Database {     get { return database ?? (database = DatabaseFactory.Get()); } } public virtual void Add(T entity) {     dbset.Add(entity);            }        public virtual void Delete(T entity) {     dbset.Remove(entity); }   public virtual T GetById(long id) {     return dbset.Find(id); }   public virtual IEnumerable<T> All() {     return dbset.ToList(); } }   DatabaseFactory class public class DatabaseFactory : Disposable, IDatabaseFactory {     private MyFinanceContext database;     public MyFinanceContext Get()     {         return database ?? (database = new MyFinanceContext());     }     protected override void DisposeCore()     {         if (database != null)             database.Dispose();     } } Unit of Work If you are new to Unit of Work pattern, checkout Fowler’s article on Unit of Work . According to Martin Fowler, the Unit of Work pattern "maintains a list of objects affected by a business transaction and coordinates the writing out of changes and the resolution of concurrency problems." Let’s create a class for handling Unit of Work   public interface IUnitOfWork {     void Commit(); }   UniOfWork class public class UnitOfWork : IUnitOfWork {     private readonly IDatabaseFactory databaseFactory;     private MyFinanceContext dataContext;       public UnitOfWork(IDatabaseFactory databaseFactory)     {         this.databaseFactory = databaseFactory;     }       protected MyFinanceContext DataContext     {         get { return dataContext ?? (dataContext = databaseFactory.Get()); }     }       public void Commit()     {         DataContext.Commit();     } }   The Commit method of the UnitOfWork will call the commit method of MyFinanceContext class and it will execute the SaveChanges method of DbContext class.   Repository class for Category In this post, we will be focusing on the persistence against Category entity and will working on other entities in later post. Let’s create a repository for handling CRUD operations for Category using derive from a generic Repository RepositoryBase<T>.   public class CategoryRepository: RepositoryBase<Category>, ICategoryRepository     {     public CategoryRepository(IDatabaseFactory databaseFactory)         : base(databaseFactory)         {         }                } public interface ICategoryRepository : IRepository<Category> { } If we need additional methods than generic repository for the Category, we can define in the CategoryRepository. Dependency Injection using Unity 2.0 If you are new to Inversion of Control/ Dependency Injection or Unity, please have a look on my articles at http://weblogs.asp.net/shijuvarghese/archive/tags/IoC/default.aspx. I want to create a custom lifetime manager for Unity to store container in the current HttpContext.   public class HttpContextLifetimeManager<T> : LifetimeManager, IDisposable {     public override object GetValue()     {         return HttpContext.Current.Items[typeof(T).AssemblyQualifiedName];     }     public override void RemoveValue()     {         HttpContext.Current.Items.Remove(typeof(T).AssemblyQualifiedName);     }     public override void SetValue(object newValue)     {         HttpContext.Current.Items[typeof(T).AssemblyQualifiedName] = newValue;     }     public void Dispose()     {         RemoveValue();     } }   Let’s create controller factory for Unity in the ASP.NET MVC 3 application. public class UnityControllerFactory : DefaultControllerFactory { IUnityContainer container; public UnityControllerFactory(IUnityContainer container) {     this.container = container; } protected override IController GetControllerInstance(RequestContext reqContext, Type controllerType) {     IController controller;     if (controllerType == null)         throw new HttpException(                 404, String.Format(                     "The controller for path '{0}' could not be found" +     "or it does not implement IController.",                 reqContext.HttpContext.Request.Path));       if (!typeof(IController).IsAssignableFrom(controllerType))         throw new ArgumentException(                 string.Format(                     "Type requested is not a controller: {0}",                     controllerType.Name),                     "controllerType");     try     {         controller= container.Resolve(controllerType) as IController;     }     catch (Exception ex)     {         throw new InvalidOperationException(String.Format(                                 "Error resolving controller {0}",                                 controllerType.Name), ex);     }     return controller; }   }   Configure contract and concrete types in Unity Let’s configure our contract and concrete types in Unity for resolving our dependencies.   private void ConfigureUnity() {     //Create UnityContainer               IUnityContainer container = new UnityContainer()                 .RegisterType<IDatabaseFactory, DatabaseFactory>(new HttpContextLifetimeManager<IDatabaseFactory>())     .RegisterType<IUnitOfWork, UnitOfWork>(new HttpContextLifetimeManager<IUnitOfWork>())     .RegisterType<ICategoryRepository, CategoryRepository>(new HttpContextLifetimeManager<ICategoryRepository>());                 //Set container for Controller Factory                ControllerBuilder.Current.SetControllerFactory(             new UnityControllerFactory(container)); }   In the above ConfigureUnity method, we are registering our types onto Unity container with custom lifetime manager HttpContextLifetimeManager. Let’s call ConfigureUnity method in the Global.asax.cs for set controller factory for Unity and configuring the types with Unity.   protected void Application_Start() {     AreaRegistration.RegisterAllAreas();     RegisterGlobalFilters(GlobalFilters.Filters);     RegisterRoutes(RouteTable.Routes);     ConfigureUnity(); }   Developing web application using ASP.NET MVC 3 We have created our domain model for our web application and also have created repositories and configured dependencies with Unity container. Now we have to create controller classes and views for doing CRUD operations against the Category entity. Let’s create controller class for Category Category Controller   public class CategoryController : Controller {     private readonly ICategoryRepository categoryRepository;     private readonly IUnitOfWork unitOfWork;           public CategoryController(ICategoryRepository categoryRepository, IUnitOfWork unitOfWork)     {         this.categoryRepository = categoryRepository;         this.unitOfWork = unitOfWork;     }       public ActionResult Index()     {         var categories = categoryRepository.All();         return View(categories);     }     [HttpGet]     public ActionResult Edit(int id)     {         var category = categoryRepository.GetById(id);         return View(category);     }       [HttpPost]     public ActionResult Edit(int id, FormCollection collection)     {         var category = categoryRepository.GetById(id);         if (TryUpdateModel(category))         {             unitOfWork.Commit();             return RedirectToAction("Index");         }         else return View(category);                 }       [HttpGet]     public ActionResult Create()     {         var category = new Category();         return View(category);     }           [HttpPost]     public ActionResult Create(Category category)     {         if (!ModelState.IsValid)         {             return View("Create", category);         }                     categoryRepository.Add(category);         unitOfWork.Commit();         return RedirectToAction("Index");     }       [HttpPost]     public ActionResult Delete(int  id)     {         var category = categoryRepository.GetById(id);         categoryRepository.Delete(category);         unitOfWork.Commit();         var categories = categoryRepository.All();         return PartialView("CategoryList", categories);       }        }   Creating Views in Razor Now we are going to create views in Razor for our ASP.NET MVC 3 application.  Let’s create a partial view CategoryList.cshtml for listing category information and providing link for Edit and Delete operations. CategoryList.cshtml @using MyFinance.Helpers; @using MyFinance.Domain; @model IEnumerable<Category>      <table>         <tr>         <th>Actions</th>         <th>Name</th>          <th>Description</th>         </tr>     @foreach (var item in Model) {             <tr>             <td>                 @Html.ActionLink("Edit", "Edit",new { id = item.CategoryId })                 @Ajax.ActionLink("Delete", "Delete", new { id = item.CategoryId }, new AjaxOptions { Confirm = "Delete Expense?", HttpMethod = "Post", UpdateTargetId = "divCategoryList" })                           </td>             <td>                 @item.Name             </td>             <td>                 @item.Description             </td>         </tr>          }       </table>     <p>         @Html.ActionLink("Create New", "Create")     </p> The delete link is providing Ajax functionality using the Ajax.ActionLink. This will call an Ajax request for Delete action method in the CategoryCotroller class. In the Delete action method, it will return Partial View CategoryList after deleting the record. We are using CategoryList view for the Ajax functionality and also for Index view using for displaying list of category information. Let’s create Index view using partial view CategoryList  Index.chtml @model IEnumerable<MyFinance.Domain.Category> @{     ViewBag.Title = "Index"; }    <h2>Category List</h2>    <script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.min.js")" type="text/javascript"></script>    <div id="divCategoryList">               @Html.Partial("CategoryList", Model) </div>   We can call the partial views using Html.Partial helper method. Now we are going to create View pages for insert and update functionality for the Category. Both view pages are sharing common user interface for entering the category information. So I want to create an EditorTemplate for the Category information. We have to create the EditorTemplate with the same name of entity object so that we can refer it on view pages using @Html.EditorFor(model => model) . So let’s create template with name Category. Let’s create view page for insert Category information   @model MyFinance.Domain.Category   @{     ViewBag.Title = "Save"; }   <h2>Create</h2>   <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>   @using (Html.BeginForm()) {     @Html.ValidationSummary(true)     <fieldset>         <legend>Category</legend>                @Html.EditorFor(model => model)               <p>             <input type="submit" value="Create" />         </p>     </fieldset> }   <div>     @Html.ActionLink("Back to List", "Index") </div> ViewStart file In Razor views, we can add a file named _viewstart.cshtml in the views directory  and this will be shared among the all views with in the Views directory. The below code in the _viewstart.cshtml, sets the Layout page for every Views in the Views folder.      @{     Layout = "~/Views/Shared/_Layout.cshtml"; }   Source Code You can download the source code from http://efmvc.codeplex.com/ . The source will be refactored on over time.   Summary In this post, we have created a simple web application using ASP.NET MVC 3 and EF Code First. We have discussed on technologies and practices such as ASP.NET MVC 3, Razor, EF Code First, Unity 2, generic Repository and Unit of Work. In my later posts, I will modify the application and will be discussed on more things. Stay tuned to my blog  for more posts on step by step application building.

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  • Programming doesn&rsquo;t have to be Magic

    - by Wes McClure
    In the show LOST, the Swan Station had a button that “had to be pushed” every 100 minutes to avoid disaster.  Several characters in the show took it upon themselves to have faith and religiously push the button, resetting the clock and averting the unknown “disaster”.  There are striking similarities in this story to the code we write every day.  Here are some common ones that I encounter: “I don’t know what it does but the application doesn’t work without it” “I added that code because I saw it in other similar places, I didn’t understand it, but thought it was necessary.” (for consistency, or to make things “work”) “An error message recommended it” “I copied that code” (and didn’t look at what it was doing) “It was suggested in a forum online and it fixed my problem so I left it” In all of these cases we haven’t done our due diligence to understand what the code we are writing is actually doing.  In the rush to get things done it seems like we’re willing to push any button (add any line of code) just to get our desired result and move on.  All of the above explanations are common things we encounter, and are valid ways to work through a problem we have, but when we find a solution to a task we are working on (whether a bug or a feature), we should take a moment to reflect on what we don’t understand.  Remove what isn’t necessary, comprehend and simplify what is.  Why is it detrimental to commit code we don’t understand? Perpetuates unnecessary code If you copy code that isn’t necessary, someone else is more likely to do so, especially peers Perpetuates tech debt Adding unnecessary code leads to extra code that must be understood, maintained and eventually cleaned up in longer lived projects Tech debt begets tech debt as other developers copy or use this code as guidelines in similar situations Increases maintenance How do we know the code is simplified if we don’t understand it? Perpetuates a lack of ownership Makes it seem ok to commit anything so long as it “gets the job done” Perpetuates the notion that programming is magic If we don’t take the time to understand every line of code we add, then we are contributing to the notion that it is simply enough to make the code work, regardless of how. TLDR Don’t commit code that you don’t understand, take the time to understand it, simplify it and then commit it!

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  • T4 Performance Counters explained

    - by user13346607
    Now that T4 is out for a few month some people might have wondered what details of the new pipeline you can monitor. A "cpustat -h" lists a lot of events that can be monitored, and only very few are self-explanatory. I will try to give some insight on all of them, some of these "PIC events" require an in-depth knowledge of T4 pipeline. Over time I will try to explain these, for the time being these events should simply be ignored. (Side note: some counters changed from tape-out 1.1 (*only* used in the T4 beta program) to tape-out 1.2 (used in the systems shipping today) The table only lists the tape-out 1.2 counters) 0 0 1 1058 6033 Oracle Microelectronics 50 14 7077 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} pic name (cpustat) Prose Comment Sel-pipe-drain-cycles, Sel-0-[wait|ready], Sel-[1,2] Sel-0-wait counts cycles a strand waits to be selected. Some reasons can be counted in detail; these are: Sel-0-ready: Cycles a strand was ready but not selected, that can signal pipeline oversubscription Sel-1: Cycles only one instruction or µop was selected Sel-2: Cycles two instructions or µops were selected Sel-pipe-drain-cycles: cf. PRM footnote 8 to table 10.2 Pick-any, Pick-[0|1|2|3] Cycles one, two, three, no or at least one instruction or µop is picked Instr_FGU_crypto Number of FGU or crypto instructions executed on that vcpu Instr_ld dto. for load Instr_st dto. for store SPR_ring_ops dto. for SPR ring ops Instr_other dto. for all other instructions not listed above, PRM footnote 7 to table 10.2 lists the instructions Instr_all total number of instructions executed on that vcpu Sw_count_intr Nr of S/W count instructions on that vcpu (sethi %hi(fc000),%g0 (whatever that is))  Atomics nr of atomic ops, which are LDSTUB/a, CASA/XA, and SWAP/A SW_prefetch Nr of PREFETCH or PREFETCHA instructions Block_ld_st Block loads or store on that vcpu IC_miss_nospec, IC_miss_[L2_or_L3|local|remote]\ _hit_nospec Various I$ misses, distinguished by where they hit. All of these count per thread, but only primary events: T4 counts only the first occurence of an I$ miss on a core for a certain instruction. If one strand misses in I$ this miss is counted, but if a second strand on the same core misses while the first miss is being resolved, that second miss is not counted This flavour of I$ misses counts only misses that are caused by instruction that really commit (note the "_nospec") BTC_miss Branch target cache miss ITLB_miss ITLB misses (synchronously counted) ITLB_miss_asynch dto. but asynchronously [I|D]TLB_fill_\ [8KB|64KB|4MB|256MB|2GB|trap] H/W tablewalk events that fill ITLB or DTLB with translation for the corresponding page size. The “_trap” event occurs if the HWTW was not able to fill the corresponding TLB IC_mtag_miss, IC_mtag_miss_\ [ptag_hit|ptag_miss|\ ptag_hit_way_mismatch] I$ micro tag misses, with some options for drill down Fetch-0, Fetch-0-all fetch-0 counts nr of cycles nothing was fetched for this particular strand, fetch-0-all counts cycles nothing was fetched for all strands on a core Instr_buffer_full Cycles the instruction buffer for a strand was full, thereby preventing any fetch BTC_targ_incorrect Counts all occurences of wrongly predicted branch targets from the BTC [PQ|ROB|LB|ROB_LB|SB|\ ROB_SB|LB_SB|RB_LB_SB|\ DTLB_miss]\ _tag_wait ST_q_tag_wait is listed under sl=20. These counters monitor pipeline behaviour therefore they are not strand specific: PQ_...: cycles Rename stage waits for a Pick Queue tag (might signal memory bound workload for single thread mode, cf. Mail from Richard Smith) ROB_...: cycles Select stage waits for a ROB (ReOrderBuffer) tag LB_...: cycles Select stage waits for a Load Buffer tag SB_...: cycles Select stage waits for Store Buffer tag combinations of the above are allowed, although some of these events can overlap, the counter will only be incremented once per cycle if any of these occur DTLB_...: cycles load or store instructions wait at Pick stage for a DTLB miss tag [ID]TLB_HWTW_\ [L2_hit|L3_hit|L3_miss|all] Counters for HWTW accesses caused by either DTLB or ITLB misses. Canbe further detailed by where they hit IC_miss_L2_L3_hit, IC_miss_local_remote_remL3_hit, IC_miss I$ prefetches that were dropped because they either miss in L2$ or L3$ This variant counts misses regardless if the causing instruction commits or not DC_miss_nospec, DC_miss_[L2_L3|local|remote_L3]\ _hit_nospec D$ misses either in general or detailed by where they hit cf. the explanation for the IC_miss in two flavours for an explanation of _nospec and the reasoning for two DC_miss counters DTLB_miss_asynch counts all DTLB misses asynchronously, there is no way to count them synchronously DC_pref_drop_DC_hit, SW_pref_drop_[DC_hit|buffer_full] L1-D$ h/w prefetches that were dropped because of a D$ hit, counted per core. The others count software prefetches per strand [Full|Partial]_RAW_hit_st_[buf|q] Count events where a load wants to get data that has not yet been stored, i. e. it is still inside the pipeline. The data might be either still in the store buffer or in the store queue. If the load's data matches in the SB and in the store queue the data in buffer takes precedence of course since it is younger [IC|DC]_evict_invalid, [IC|DC|L1]_snoop_invalid, [IC|DC|L1]_invalid_all Counter for invalidated cache evictions per core St_q_tag_wait Number of cycles pipeline waits for a store queue tag, of course counted per core Data_pref_[drop_L2|drop_L3|\ hit_L2|hit_L3|\ hit_local|hit_remote] Data prefetches that can be further detailed by either why they were dropped or where they did hit St_hit_[L2|L3], St_L2_[local|remote]_C2C, St_local, St_remote Store events distinguished by where they hit or where they cause a L2 cache-to-cache transfer, i.e. either a transfer from another L2$ on the same die or from a different die DC_miss, DC_miss_\ [L2_L3|local|remote]_hit D$ misses either in general or detailed by where they hit cf. the explanation for the IC_miss in two flavours for an explanation of _nospec and the reasoning for two DC_miss counters L2_[clean|dirty]_evict Per core clean or dirty L2$ evictions L2_fill_buf_full, L2_wb_buf_full, L2_miss_buf_full Per core L2$ buffer events, all count number of cycles that this state was present L2_pipe_stall Per core cycles pipeline stalled because of L2$ Branches Count branches (Tcc, DONE, RETRY, and SIT are not counted as branches) Br_taken Counts taken branches (Tcc, DONE, RETRY, and SIT are not counted as branches) Br_mispred, Br_dir_mispred, Br_trg_mispred, Br_trg_mispred_\ [far_tbl|indir_tbl|ret_stk] Counter for various branch misprediction events.  Cycles_user counts cycles, attribute setting hpriv, nouser, sys controls addess space to count in Commit-[0|1|2], Commit-0-all, Commit-1-or-2 Number of times either no, one, or two µops commit for a strand. Commit-0-all counts number of times no µop commits for the whole core, cf. footnote 11 to table 10.2 in PRM for a more detailed explanation on how this counters interacts with the privilege levels

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  • Automating release management and CI on python projects under mercurial VCS

    - by ms4py
    I have a set of Python projects which are under the mercurial VCS. I would like to automate the following tasks: Run the test suite for every commit (CI). Make a source distribution for every commit, which has a tag in mercurial. This is regarded as a new release. Copy the distribution to a special repository. There is Jenkins as a proposal for similar questions, but I'm not sure if it can handle the release management like intended.

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  • GarageBand w/ Git?

    - by jrc03c
    I'm trying to put a GarageBand project under version control with Git, but I've noticed that every time I make changes to my song and try to add and commit, Git claims that "there are no changes to commit" and that "everything is up-to-date." Is this because GarageBand files are binary or something weird that Git can't properly track? Or do I need to add some special flags to my Git commands? Thanks for the help!

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  • Rebasing a branch which is public

    - by Dror
    I'm failing to understand how to use git-rebase, and I consider the following example. Let's start a repository in ~/tmp/repo: $ git init Then add a file foo $ echo "hello world" > foo which is then added and committed: $ git add foo $ git commit -m "Added foo" Next, I started a remote repository. In ~/tmp/bare.git I ran $ git init --bare In order to link repo to bare.git I ran $ git remote add origin ../bare.git/ $ git push --set-upstream origin master Next, lets branch, add a file and set an upstream for the new branch b1: $ git checkout -b b1 $ echo "bar" > foo2 $ git add foo2 $ git commit -m "add foo2 in b1" $ git push --set-upstream origin b1 Now it is time to switch back to master and change something there: $ echo "change foo" > foo $ git commit -a -m "changed foo in master" $ git push At this point in master the file foo contain changed foo, while in b1 it is still hello world. Finally, I want to sync b1 with the progress made in master. $ git checkout b1 $ git fetch origin $ git rebase origin/master At this point git st returns: # On branch b1 # Your branch and 'origin/b1' have diverged, # and have 2 and 1 different commit each, respectively. # (use "git pull" to merge the remote branch into yours) # nothing to commit, working directory clean At this point the content of foo in the branch b1 is change foo as well. So what does this warning mean? I expected I should do a git push, git suggests to do git pull... According to this answer, this is more or less it, and in his comment @FrerichRaabe explicitly say that I don't need to do a pull. What's going on here? What is the danger, how should one proceed? How should the history be kept consistent? What is the interplay between the case described above and the following citation: Do not rebase commits that you have pushed to a public repository. taken from pro git book. I guess it is somehow related, and if not I would love to know why. What's the relation between the above scenario and the procedure I described in this post.

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  • JavaScript Coding for Finding Shipping Total

    - by user2913279
    I am having a very hard time with this code. I have been working on it for days and cannot seem to figure it out. Please help!! Here are the specific I need for the code: Many companies normally charge a shipping and handling charge for purchases. Create a Web page that allows a user to enter a purchase price into a text box and includes a JavaScript function that calculates shipping and handling. Add functionality to the script that adds a minimum shipping and handling charge of $1.50 for any purchase that is less than or equal to $25.00. For any orders over $25.00, add 10% to the total purchase price for shipping and handling, but do not include the $1.50 minimum shipping and handling charge. The formula for calculating a percentage is price * percent / 100. For example, the formula for calculating 10% of a $50.00 purchase price is 50 * 10 / 100, which results in a shipping and handling charge of $5.00. After you determine the total cost of the order (purchase plus shipping and handling), display it in an alert dialog box. Here is the code I have: <!DOCTYPE> <head> <title>Calculate Shipping</title> <script type="text/javascript"> function parseInt() { var salesPrice = document.salesForm.Price.value; var minCharge = salesPrice + 1.50; var shipping = salesPrice * 10/100; if (salesPrice <= 25) window.alert('Your sales total including shipping is $' + minCharge); else window.alert('Your sales total including shipping is $' + salesPrice + shipping); } </script> </head> <body> <form name="salesForm"> <div > <p>Enter Your Purchase Price</p> <input type="text" name="Price" /><br /><br /> <input type="button" name="Calculate" value="Calculate Shipping" onclick="parseInt ()" /> </div> </form> </body> </html> Everything works except for the math in the alert box. It will show an incorrect total...

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  • Great Customer Service Example

    - by MightyZot
    A few days ago I wrote about what I consider a poor customer service interaction with TiVo, a company that I have been faithful to for the past 12 years or so. In that post I talked about how they helped me, but I felt like I was doing something wrong at the end of the call – when in reality I was just following through with an offer that TiVo made possible through my cable company. Today I had a wonderful customer service interaction with American Express, another company that I have been loyal to for many years.(I am a Gold Card member.) I like my Amex card because I can use it for big purchases and it forces me to pay them off at the end of the month. Well, the reality is that I’m not always so good at doing that, so sometimes my payments are over a couple of months.  :) A few days ago I received an email from “American Express” fraud detection. The email stated that I should call a toll free number and have the last four digits of my card handy. I grew up during the BBS era with some creative and somewhat mischievous friends. I’ve learned to be extremely cautious with regard to my online life! So, I did what you would expect…I sent them a nice reply that said “Go screw yourself.” For the past couple of days someone has been trying to call me and I assumed it was the same prankster trying to get the last four digits of my card. The last caller left a message indicating that they were from American Express and they wanted to talk to me about my card. After looking up their customer service numbers on the www.americanexpress.com web site, I called and was put through to the fraud detection group. The rep explained that there were some charges on my wife’s card that did not fit our purchase profile. She went through each charge and, for the most part, they looked like charges my wife may have made. My wife had asked to use the card for some Christmas shopping during the same timeframe as the charges. The American Express rep very politely explained that these looked out of character to her. She continued through the charges. She listed a charge for $160 – at this point my adrenaline started kicking in. My wife said she was going to charge about $25 or $30 dollars, not $160. Next, the rep listed a charge for over $1200. Uh oh!! Now I know that my account has been compromised. I informed the rep that we definitely did not make those charges. She replied with, “that’s ok Mr Pope, we declined those charges as well as some others.” We went through the pending charges and there were a couple more that were questionable. The rep very patiently waited while I called my wife on my office phone to verify the charges. Sure enough, my wife had not ordered anything from Netflix or purchased anything with Yahoo Wallet! “No problem Mr Pope, we will remove those charges as well.” “We are going to cancel your wife’s card and send her a new one. She will receive it by 7pm tomorrow via Federal Express. Please watch your statements over the next couple of months. If you notice anything fishy, give us a call and we will take care of it for you.” (Wow, I’m thinking to myself!) “Is there anything else I can help you with Mr Pope?” “Nope, thank you very much for catching this so early and declining those charges!”, I said smiling. Apparently she could hear me smiling on the other end of the phone line because she replied with “keep smiling Mr Pope and have a good rest of your week.” Now THAT’s customer service!  Thank you American Express!!! I shall remain an ever faithful customer. Interesting…

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  • Is it possible for the Subversion Apache module to serve html files with an html content-type without using the svn:mime-type property?

    - by Martin Pain
    I am aware that if you set the svn:mime-type Subversion property on a .html file to text/html then when viewing the file in a browser through the Subversion module in Apache httpd it will be served with a Content-Type: text/html header, enabling the browser to render it as HTML rather than plain text. However, I am looking for a way to do this without using the svn:mime-type property. I'm aware that you can configure your svn client to automatically add the property - this is not what I want, as I do not want to ensure all users have these settings. I'm also aware that I could create a pre-commit hook that rejects the commit if the properties are not set, in order to force users to set the property - I might fall back to that, but I'm looking for something less intrusive. I'm also aware that I could use a post-commit hook to add the properties automatically on the server-side. I'd rather not do that (as users then have to update immediately after their commit, and it's not trivial to write) - I'm looking for a better alternative. Perhaps something with rewrite rules in the Apache server?

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  • OpenVPN server will not redirect traffic

    - by skerit
    I set up an OpenVPN server on my VPS, using this guide: http://vpsnoc.com/blog/how-to-install-openvpn-on-a-debianubuntu-vps-instantly/ And I can connect to it without problems. Connect, that is, because no traffic is being redirected. When I try to load a webpage when connected to the vpn I just get an error. This is the config file it generated: dev tun server 10.8.0.0 255.255.255.0 ifconfig-pool-persist ipp.txt ca ca.crt cert server.crt key server.key dh dh1024.pem push "route 10.8.0.0 255.255.255.0" push "redirect-gateway" comp-lzo keepalive 10 60 ping-timer-rem persist-tun persist-key group daemon daemon This is my iptables.conf # Generated by iptables-save v1.4.4 on Sat May 7 13:09:44 2011 *raw :PREROUTING ACCEPT [37938267:10998335127] :OUTPUT ACCEPT [35616847:14165347907] COMMIT # Completed on Sat May 7 13:09:44 2011 # Generated by iptables-save v1.4.4 on Sat May 7 13:09:44 2011 *nat :PREROUTING ACCEPT [794948:91051460] :POSTROUTING ACCEPT [1603974:108147033] :OUTPUT ACCEPT [1603974:108147033] -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE -A POSTROUTING -s 10.8.0.0/24 -o eth1 -j MASQUERADE -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j MASQUERADE COMMIT # Completed on Sat May 7 13:09:44 2011 # Generated by iptables-save v1.4.4 on Sat May 7 13:09:44 2011 *mangle :PREROUTING ACCEPT [37938267:10998335127] :INPUT ACCEPT [37677226:10960834925] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [35616847:14165347907] :POSTROUTING ACCEPT [35680187:14169930490] COMMIT # Completed on Sat May 7 13:09:44 2011 # Generated by iptables-save v1.4.4 on Sat May 7 13:09:44 2011 *filter :INPUT ACCEPT [37677226:10960834925] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [35616848:14165347947] -A INPUT -i eth0 -j LOG --log-prefix "BANDWIDTH_IN:" --log-level 7 -A FORWARD -o eth0 -j LOG --log-prefix "BANDWIDTH_OUT:" --log-level 7 -A FORWARD -i eth0 -j LOG --log-prefix "BANDWIDTH_IN:" --log-level 7 -A OUTPUT -o eth0 -j LOG --log-prefix "BANDWIDTH_OUT:" --log-level 7 COMMIT # Completed on Sat May 7 13:09:44 2011

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  • Export files to remote server using TortoiseSVN

    - by Matt
    Hi, I'm using TortoiseSVN to keep revisions of my code. When I commit changes, I take note of what files have changed and upload them to my server using FTP. Here's my workflow: Edit files on local computer (eg. files in C:\Users\Me\web) Commit changes to local repository using rightclick- TortoiseSVN- SVN Commit. Take the files, open FileZilla (FTP client) and upload the files to a remote server. I was wondering if there was a way in which I could omit step 3 from my workflow. Basically I would like the changed files to be automatically uploaded to the remote server when I commit a version to the repository. Information about my computer environment: Windows 7 Ultimate x64 with TortoiseSVN x64 Notepad++ text editor Files edited are PHP, CSS, JS, HTML, etc. Server is running Linux with PHP 5.2 and MySQL. FileZilla is used to upload files. I can connect to the server via SSH if that is needed. Thank you in advance.

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  • Host is missing hostname and/or domain

    - by anlawang
    i use puppet 0.25.4 on ubuntu 10.04,when puppet installed ,i got the infor below : Nov 29 10:30:30 puppet puppetmasterd[4422]: Host is missing hostname and/or domain: pclient.example.com Nov 29 10:30:30 puppet puppetmasterd[4422]: Compiled catalog for pclient.example.com in 0.02 seconds i dont know how to fix it ,who can help me thank you ! my configuration : I use apt-get to install the puppet,so some configuration have been fixed puppet.conf on client : > [main] server=puppet.example.com > logdir=/var/log/puppet > vardir=/var/lib/puppet > ssldir=/var/lib/puppet/ssl > rundir=/var/run/puppet > factpath=$vardir/lib/facter > pluginsync=false > templatedir=$confdir/templates > prerun_command=/etc/puppet/etckeeper-commit-pre > postrun_command=/etc/puppet/etckeeper-commit-post > certname=pclient.example.com > node_name=cert [puppetd] > runinterval=30 puppet.conf on server: > [main] logdir=/var/log/puppet > vardir=/var/lib/puppet > ssldir=/var/lib/puppet/ssl > rundir=/var/run/puppet > factpath=$vardir/lib/facter > pluginsync=true > templatedir=$confdir/templates > prerun_command=/etc/puppet/etckeeper-commit-pre > postrun_command=/etc/puppet/etckeeper-commit-post i user the default node on site.pp i am a newer to puppet,so i dont know the reason for these problems!! thank you again!!!

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  • How to make Windows command prompt treat single quote as though it is a double quote?

    - by mark
    My scenario is simple - I am copying script samples from the Mercurial online book (at http://hGBook.red-bean.com) and pasting them in a Windows command prompt. The problem is that the samples in the book use single quoted strings. When a single quoted string is passed on the Windows command prompt, the latter does not recognize that everything between the single quotes belongs to one string. For example, the following command: hg commit -m 'Initial commit' cannot be pasted as is in a command prompt, because the latter treats 'Initial commit' as two strings - 'Initial and commit'. I have to edit the command after paste and it is annoying. Is it possible to instruct the Windows command prompt to treat single quotes similarly to the double one? EDIT Following the reply by JdeBP I have done a little research. Here is the summary: Mercurial entry point looks like so (it is a python program): def run(): "run the command in sys.argv" sys.exit(dispatch(request(sys.argv[1:]))) So, I have created a tiny python program to mimic the command line processing used by mercurial: import sys print sys.argv[1:] Here is the Unix console log: [hg@Quake ~]$ python 1.py "1 2 3" ['1 2 3'] [hg@Quake ~]$ python 1.py '1 2 3' ['1 2 3'] [hg@Quake ~]$ python 1.py 1 2 3 ['1', '2', '3'] [hg@Quake ~]$ And here is the respective Windows console log: C:\Workpython 1.py "1 2 3" ['1 2 3'] C:\Workpython 1.py '1 2 3' ["'1", '2', "3'"] C:\Workpython 1.py 1 2 3 ['1', '2', '3'] C:\Work One can clearly see that Windows does not treat single quotes as double quotes. And this is the essence of my question.

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  • Export files to remote server using TortoiseSVN

    - by Matt
    I'm using TortoiseSVN to keep revisions of my code. When I commit changes, I take note of what files have changed and upload them to my server using FTP. Here's my workflow: Edit files on local computer (eg. files in C:\Users\Me\web) Commit changes to local repository using rightclick- TortoiseSVN- SVN Commit. Take the files, open FileZilla (FTP client) and upload the files to a remote server. I was wondering if there was a way in which I could omit step 3 from my workflow. Basically I would like the changed files to be automatically uploaded to the remote server when I commit a version to the repository. Information about my computer environment: Windows 7 Ultimate x64 with TortoiseSVN x64 Notepad++ text editor Files edited are PHP, CSS, JS, HTML, etc. Server is running Linux with PHP 5.2 and MySQL. FileZilla is used to upload files. I can connect to the server via SSH if that is needed. Thank you in advance.

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  • Cron job checking for changes in Git repository

    - by HNygard
    We have just moved our server configs to a Git repository. Therefore there should not be any changes in any of the repository folders. I was thinking about how I could set up a cron job to check for any uncommited changes. How could a cron job be set up to check for changes in a Git repository? Greping the output of the git status command might just do it. Grep and cron jobs are not my strong side. Here are some sample outputs from git status: Standing the folder containing the git repository (e.g. /path/gitrepo/) with changed files: $ git status # On branch master # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: apache2/sites-enabled/000-default # # Untracked files: # (use "git add <file>..." to include in what will be committed) # # apache2/conf.d/test no changes added to commit (use "git add" and/or "git commit -a") Standing in the folder when there is no changes: $ git status # On branch master nothing to commit (working directory clean) Update: Synced up with origin is not important. There should be no local changes. Local files that must be in place go into the .gitignore file. In addition to the server configs there are also git repos for content (static web sites, web apps, wordpress, etc). None of the repositories should have local changes. We might use Puppet in the long run since its being used for development of one of the web apps.

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  • cygwin fork error

    - by Techie Help
    I have set up a new PC and installed cygwin on it. Its windows 7 pro. Whenever I try to build our application on it, I get the following error: 0 [main] sh 3472 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 /bin/sh: fork: retry: Resource temporarily unavailable 0 [main] sh 3220 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 /bin/sh: fork: retry: Resource temporarily unavailable 0 [main] sh 4896 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 /bin/sh: fork: retry: Resource temporarily unavailable 0 [main] sh 4884 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 It prints this few times and then dies. I have already done a lot of research on this problem. I have already uninstalled and installed cygwin more than 5 times. Done rebaseall everytime I installed it. Checked for possible BLODA, I had notron antivirus, which I have removed. As an aside, I tried posting this question to cygwin mailing list after subscribing to it. But my mail does not appear on the list. I suppose they want address to be munged and I have no clue how to do it. supposedly, they are treating it as a spam. Any idea how I can post to the mailing list there.

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  • Payment Processors - What do I need to know if I want to accept credit cards on my website?

    - by Michael Pryor
    This question talks about different payment processors and what they cost, but I'm looking for the answer to what do I need to do if I want to accept credit card payments? Assume I need to store credit card numbers for customers, so that the obvious solution of relying on the credit card processor to do the heavy lifting is not available. PCI Data Security, which is apparently the standard for storing credit card info, has a bunch of general requirements, but how does one implement them? And what about the vendors, like Visa, who have their own best practices? Do I need to have keyfob access to the machine? What about physically protecting it from hackers in the building? Or even what if someone got their hands on the backup files with the sql server data files on it? What about backups? Are there other physical copies of that data around? Tip: If you get a merchant account, you should negotiate that they charge you "interchange-plus" instead of tiered pricing. With tiered pricing, they will charge you different rates based on what type of Visa/MC is used -- ie. they charge you more for cards with big rewards attached to them. Interchange plus billing means you only pay the processor what Visa/MC charges them, plus a flat fee. (Amex and Discover charge their own rates directly to merchants, so this doesn't apply to those cards. You'll find Amex rates to be in the 3% range and Discover could be as low as 1%. Visa/MC is in the 2% range). This service is supposed to do the negotiation for you (I haven't used it, this is not an ad, and I'm not affiliated with the website, but this service is greatly needed.) This blog post gives a complete rundown of handling credit cards (specifically for the UK).

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  • How much does Website Development cost nowadays?

    - by Andreas Grech
    I am thinking of setting up my own freelance business but coming from a workplace that offers a particular service to huge clients, I do not know what are the current charges for websites are nowadays. I know that as technology just keeps changing and changing (most of the time, for the better...), the amount you charge for a single website is constantly differing. Like for example, I don't think static websites (with just static html pages) are that expensive today, no? (as i said, I might be mistaken since I haven't really touched on this freelance industry yet) So, freelance web-developers out there, can you give me estimates on how much you charge for your clients? Some examples of websites that I want to know an approx charge: ~10 static html pages ~10 dhtml pages (with maybe a flasy menu on the top/side) Database driven websites with a standard CMS (be it the one you developed, or an existing one) Database driven but with a custom-built cms for the particular client Using an existing template for a design Starting the design from scratch etc... I know that the normally clients don't really care about the technologies used to construct their websites, but do you charge differently according to which technology you use to build the website with?; as in, is the technology a factor when setting the price? ...being ASP.Net, PHP, Ruby On Rails etc... Also, how do you go on about charging your clients for your services? What are the major factors that you consider when setting a price tag for a website to a client ? And better yet, how do you even find prospective clients? <= [or should I leave this question for a different post?] Btw, in your post, also mention some numbers (in cash values, be it in USD, GBP, EUR or anything) because I want to be able to take calculate some averages from this post when some answers stack up

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  • Is there a standard SQL Table design for overriding 'big picture' default values with lower level de

    - by RichardHowells
    Here's an example. Suppose we are trying to calculate a service charge. Say sales in the USA attract a 10 dollar charge, sales in the UK attract a 20 dollar charge So far it's easy - we are starting to imagine a table that lists charges by country. Now lets assume that Alaska and Hawaii are treated as special cases they are both 15 dollars That suggests a table with states, Alaska and Hawaii are charged at 15, but presumably we need 48 (redundant) rows all saying 10. This gives us a maintainance problem, our user only wants to type 10 once NOT 48 times. It does not sit well with the UK either. The UK does not have states. Suppose we throw in another couple of cross cutting rules. If you order by phone there is a 10% supplement on the charge. If you order via the web there is a 10% discount. But for some reason best known to the owners of the business the web/phone supplement/discount are not applied in Hawaii. It seems to me that this is quite a common kind of problem and there is probably a well known arrangement of tables to store the data. Most cases get handled by broad brush answers, but there are some very detailed low level variations that give rise to a huge number of theoretical combinations, most of which are not used.

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  • SQL SERVER – Simple Example of Snapshot Isolation – Reduce the Blocking Transactions

    - by pinaldave
    To learn any technology and move to a more advanced level, it is very important to understand the fundamentals of the subject first. Today, we will be talking about something which has been quite introduced a long time ago but not properly explored when it comes to the isolation level. Snapshot Isolation was introduced in SQL Server in 2005. However, the reality is that there are still many software shops which are using the SQL Server 2000, and therefore cannot be able to maintain the Snapshot Isolation. Many software shops have upgraded to the later version of the SQL Server, but their respective developers have not spend enough time to upgrade themselves with the latest technology. “It works!” is a very common answer of many when they are asked about utilizing the new technology, instead of backward compatibility commands. In one of the recent consultation project, I had same experience when developers have “heard about it” but have no idea about snapshot isolation. They were thinking it is the same as Snapshot Replication – which is plain wrong. This is the same demo I am including here which I have created for them. In Snapshot Isolation, the updated row versions for each transaction are maintained in TempDB. Once a transaction has begun, it ignores all the newer rows inserted or updated in the table. Let us examine this example which shows the simple demonstration. This transaction works on optimistic concurrency model. Since reading a certain transaction does not block writing transaction, it also does not block the reading transaction, which reduced the blocking. First, enable database to work with Snapshot Isolation. Additionally, check the existing values in the table from HumanResources.Shift. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO Now, we will need two different sessions to prove this example. First Session: Set Transaction level isolation to snapshot and begin the transaction. Update the column “ModifiedDate” to today’s date. -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO Please note that we have not yet been committed to the transaction. Now, open the second session and run the following “SELECT” statement. Then, check the values of the table. Please pay attention on setting the Isolation level for the second one as “Snapshot” at the same time when we already start the transaction using BEGIN TRAN. -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values in the table are still original values. They have not been modified yet. Once again, go back to session 1 and begin the transaction. -- Session 1 COMMIT After that, go back to Session 2 and see the values of the table. -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that the values are yet not changed and they are still the same old values which were there right in the beginning of the session. Now, let us commit the transaction in the session 2. Once committed, run the same SELECT statement once more and see what the result is. -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO You will notice that it now reflects the new updated value. I hope that this example is clear enough as it would give you good idea how the Snapshot Isolation level works. There is much more to write about an extra level, READ_COMMITTED_SNAPSHOT, which we will be discussing in another post soon. If you wish to use this transaction’s Isolation level in your production database, I would appreciate your comments about their performance on your servers. I have included here the complete script used in this example for your quick reference. ALTER DATABASE AdventureWorks SET ALLOW_SNAPSHOT_ISOLATION ON GO SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN UPDATE HumanResources.Shift SET ModifiedDate = GETDATE() GO -- Session 2 SET TRANSACTION ISOLATION LEVEL SNAPSHOT BEGIN TRAN SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 1 COMMIT -- Session 2 SELECT ModifiedDate FROM HumanResources.Shift GO -- Session 2 COMMIT SELECT ModifiedDate FROM HumanResources.Shift GO Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Transaction Isolation

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