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• Oracle Enterprise Manager 12c Configuration Best Practices (Part 3 of 3)

  - by Bethany Lapaglia

  <span id="XinhaEditingPostion"></span>&amp;lt;span id=&amp;quot;XinhaEditingPostion&amp;quot;&amp;gt;&amp;lt;/span&amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;span id=&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;XinhaEditingPostion&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/span&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; This is part 3 of a three-part blog series that summarizes the most commonly implemented configuration changes to improve performance and operation of a large Enterprise Manager 12c environment. A “large” environment is categorized by the number of agents, targets and users. See the Oracle Enterprise Manager Cloud Control Advanced Installation and Configuration Guide chapter on Sizing for more details on sizing your environment properly. Part 1 of this series covered recommended configuration changes for the OMS and Repository Part 2 covered recommended changes for the Weblogic server Part 3 covers general configuration recommendations and a few known issues The entire series can be found in the My Oracle Support note titled Oracle Enterprise Manager 12c Configuration Best Practices [1553342.1]. Configuration Recommendations Configure E-Mail Notifications for EM related Alerts In some environments, the notifications for events for different target types may be sent to different support teams (i.e. notifications on host targets may be sent to a platform support team). However, the EM application administrators should be well informed of any alerts or problems seen on the EM infrastructure components. Recommendation: Create a new Incident rule for monitoring all EM components and setup the notifications to be sent to the EM administrator(s). The notification methods available can create or update an incident, send an email or forward to an event connector. To setup the incident rule set follow the steps below. Note that each individual rule in the rule set can have different actions configured. 1.  To create an incident rule for monitoring the EM components, click on Setup / Incidents / Incident Rules. On the All Enterprise Rules page, click on the out-of-box rule called “Incident management Ruleset for all targets” and then click on the Actions drop down list and select “Create Like Rule Set…” 2. For the rule set name, enter a name such as MTM Ruleset. Under the Targets tab, select “All targets of types” and select “OMS and Repository” from the drop down list. This target type contains all of the key EM components (OMS servers, repository, domains, etc.) 3. Click on the Rules tab. To edit a rule, click on the rule name and click on Edit as seen below 4. Modify the following rules: a. Incident creation Rule for metric alerts i. Leave the Type set as is but change the Severity to add Warning by clicking on the drop down list and selecting “Warning”. Click Next. ii.  Add or modify the actions as required (i.e. add email notifications). Click Continue and then click Next. iii. Leave the Name and description the same and click Next. iv. Click Continue on the Review page. b. Incident creation Rule for target unreachable. i.   Leave the Type set as is but change the Target type to add OMS and Repository by clicking on the drop down list selecting “OMS and Repository”. Click Next. ii.  Add or modify the actions as required (i.e. add email notifications) Click Continue and then click Next. iii. Leave the Name and description the same and click Next. iv. Click Continue on the Review page. 5.  Modify the actions for any other rule as required and be sure to click the “Save” push button to save the rule set or all changes will be lost. Configure Out-of-Band Notifications for EM Agent Out-of-Band notifications act as a backup when there’s a complete EM outage or a repository database issue. This is configured on the agent of the OMS server and can be used to send emails or execute another script that would create a trouble ticket. It will send notifications about the following issues: • Repository Database down • All OMS are down • Repository side collection job that is broken or has an invalid schedule • Notification job that is broken or has an invalid schedule Recommendation: To setup Out-of-Band Notifications, refer to the MOS note “How To Setup Out Of Bound Email Notification In 12c” (Doc ID 1472854.1) Modify the Performance Test for the EM Console Service The EM Console Service has an out-of-box defined performance test that will be run to determine the status of this service. The test issues a request via an HTTP method to a specific URL. By default, the HTTP method used for this test is a GET but for performance reasons, should be changed to HEAD. The URL used for this request is set to point to a specific OMS server by default. If a multi-OMS system has been implemented and the OMS servers are behind a load balancer, then the URL in this section must be modified to point to the load balancer name instead of a specific server name. If this is not done and a portion of the infrastructure is down then the EM Console Service will show down as this test will fail. Recommendation: Modify the HTTP Method for the EM Console Service test and the URL if required following the detailed steps below. 1.  To create an incident rule for monitoring the EM components, click on Targets / Services. From the list of services, click on the EM Console Service. 2. On the EM Console Service page, click on the Test Performance tab. 3.  At the bottom of the page, click on the Web Transaction test called EM Console Service Test 4.  Click on the Service Tests and Beacons breadcrumb near the top of the page. 5.  Under the Service Tests section, make sure the EM Console Service Test is selected and click on the Edit push button. 6.  Under the Transaction section, make sure the Access Logout page transaction is selected and click on the Edit push button 7) Under the Request section, change the HTTP Method from the default of GET to the recommended value of HEAD. The URL in this section must be modified to point to the load balancer name instead of a specific server name if multi-OMSes have been implemented. Check for Known Issues Job Purge Repository Job is Shown as Down This issue is caused after upgrading EM from 12c to 12cR2. On the Repository page under Setup ? Manage Cloud Control ? Repository, the job called “Job Purge” is shown as down and the Next Scheduled Run is blank. Also, repvfy reports that this is a missing DBMS_SCHEDULER job. Recommendation: In EM 12cR2, the apply_purge_policies have been moved from the MGMT_JOB_ENGINE package to the EM_JOB_PURGE package. To remove this error, execute the commands below: $ repvfy verify core -test 2 -fix To confirm that the issue resolved, execute $ repvfy verify core -test 2 It can also be verified by refreshing the Job Service page in EM and check the status of the job, it should now be Up. Configure the Listener Targets in EM with the Listener Password (where required) EM will report this error every time it is encountered in the listener log file. In a RAC environment, typically the grid home and rdbms homes are owned by different OS users. The listener always runs from the grid home. Only the listener process owner can query or change the listener properties. The listener uses a password to allow other OS users (ex. the agent user) to query the listener process for parameters. EM has a default listener target metric that will query these properties. If the agent is not permitted to do this, the TNS incident (TNS-1190) will be logged in the listener’s log file. This means that the listener targets in EM also need to have this password set. Not doing so will cause many TNS incidents (TNS-1190). Below is a sample of this error from the listener log file: Recommendation: Set a listener password and include it in the configuration of the listener targets in EM For steps on setting the listener passwords, see MOS notes: 260986.1 , 427422.1

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• One page using querystring or many folders and pages?

  - by ClarkeyBoy

  I have an application where I have the 'core' code in one folder for which there is a virtual directory in the root, such that I can include any core files using /myApp/core/bla.asp. I then have two folders outside of this with a default.asp which currently use the querystring to define what page should be displayed. One page is for general users, the other will only be accessible to users who have permission to manage users / usergroups / permissions. The core code checks the querystring and then checks the permissions for that user. An example of this as it is now is default.asp?action=view&viewtype=list&objectid=server. I am not worried about SEO as this is an internal app and uses Windows Auth. My question is, is it better the way it is now or would it be better to have something like the following: /server/view/list/ /server/view/?id=123 /server/create/ /server/edit/?id=123 /server/remove/?id=123 In the above folders I would have a home page which defines all the variables which are currently determined by the querystring - in /server/create/ for example, I would define the action as 'create', object name as 'server' and so on. In terms of future development, I really have no idea which method would be best. I think the 2nd method would be best in terms of following what page does what but this is such a huge change to make at this stage that I would really like some opinions, preferably based on experience. PS Sorry if the tags are wrong - I am new to this forum and thought this was a bit too much of a discussion for StackOverflow as that is very much right / wrong answer based. I got the idea SE is more discussion based.

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• How to Hibernate from .NET Apps and How to enable Hibernate in Windows XP

  The usage of Computer desktop or laptop is increased all around the world phenomenally. This link gives you the picture on how power consumption is for various devices we use daily. to reduce the power consumption Hibernate is one of the best way provided by default in Windows Vista or Windows 7. Hibernate feature enables you to close the machine without closing your applications, that means the applications will be restored as they were once we restart the machine. Hibernate feature is not enabled in Windows XP by default. I’ve seen many people that they run (do not switch off) the machines months and months as they do not want to close the windows or applications running in Windows XP. below are the steps to enable Hibernate in Windows XP. Right click on Desktop. Click on properties. Go to screen save tab. Click on power button Select Hibernate tab Check the checkbox “Enabled Hibernate” Apply the settings. Now when you try to shutdown, “Shut down windows” dialog shows “Hibernate” options. Now you can safely close the machine without closing your applications or windows as they will be restored once you on the machine. </SPAN? Some time you might want to provide this future programmatically for the applications you develop for windows. Generally you might want to provide this option in windows applications where process needs huge time. Download managers are the one of the best example. below is the code to do a Hibernate from the .NET code. using System.Windows.Forms;namespace CodeKicks.WinApp.Machine{ public static class MyMachineHelper { public static void DoHibernate() { //Application.SetSuspendState(PowerState.Suspend, true, false); Application.SetSuspendState(PowerState.Hibernate, true, false); } }} span.fullpost {display:none;}

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• .NET 4: &ldquo;Slim&rdquo;-style performance boost!

  - by Vitus

  RTM version of .NET 4 and Visual Studio 2010 is available, and now we can do some test with it. Parallel Extensions is one of the most valuable part of .NET 4.0. It’s a set of good tools for easily consuming multicore hardware power. And it also contains some “upgraded” sync primitives – Slim-version. For example, it include updated variant of widely known ManualResetEvent. For people, who don’t know about it: you can sync concurrency execution of some pieces of code with this sync primitive. Instance of ManualResetEvent can be in 2 states: signaled and non-signaled. Transition between it possible by Set() and Reset() methods call. Some shortly explanation: Thread 1 Thread 2 Time mre.Reset(); mre.WaitOne(); //code execution 0 //wating //code execution 1 //wating //code execution 2 //wating //code execution 3 //wating mre.Set(); 4 //code execution //… 5 Upgraded version of this primitive is ManualResetEventSlim. The idea in decreasing performance cost in case, when only 1 thread use it. Main concept in the “hybrid sync schema”, which can be done as following:   internal sealed class SimpleHybridLock : IDisposable { private Int32 m_waiters = 0; private AutoResetEvent m_waiterLock = new AutoResetEvent(false);   public void Enter() { if (Interlocked.Increment(ref m_waiters) == 1) return; m_waiterLock.WaitOne(); }   public void Leave() { if (Interlocked.Decrement(ref m_waiters) == 0) return; m_waiterLock.Set(); }   public void Dispose() { m_waiterLock.Dispose(); } } It’s a sample from Jeffry Richter’s book “CLR via C#”, 3rd edition. Primitive SimpleHybridLock have two public methods: Enter() and Leave(). You can put your concurrency-critical code between calls of these methods, and it would executed in only one thread at the moment. Code is really simple: first thread, called Enter(), increase counter. Second thread also increase counter, and suspend while m_waiterLock is not signaled. So, if we don’t have concurrent access to our lock, “heavy” methods WaitOne() and Set() will not called. It’s can give some performance bonus. ManualResetEvent use the similar idea. Of course, it have more “smart” technics inside, like a checking of recursive calls, and so on. I want to know a real difference between classic ManualResetEvent realization, and new –Slim. I wrote a simple “benchmark”: class Program { static void Main(string[] args) { ManualResetEventSlim mres = new ManualResetEventSlim(false); ManualResetEventSlim mres2 = new ManualResetEventSlim(false);   ManualResetEvent mre = new ManualResetEvent(false);   long total = 0; int COUNT = 50;   for (int i = 0; i < COUNT; i++) { mres2.Reset(); Stopwatch sw = Stopwatch.StartNew();   ThreadPool.QueueUserWorkItem((obj) => { //Method(mres, true); Method2(mre, true); mres2.Set(); }); //Method(mres, false); Method2(mre, false);   mres2.Wait(); sw.Stop();   Console.WriteLine("Pass {0}: {1} ms", i, sw.ElapsedMilliseconds); total += sw.ElapsedMilliseconds; }   Console.WriteLine(); Console.WriteLine("==============================="); Console.WriteLine("Done in average=" + total / (double)COUNT); Console.ReadLine(); }   private static void Method(ManualResetEventSlim mre, bool value) { for (int i = 0; i < 9000000; i++) { if (value) { mre.Set(); } else { mre.Reset(); } } }   private static void Method2(ManualResetEvent mre, bool value) { for (int i = 0; i < 9000000; i++) { if (value) { mre.Set(); } else { mre.Reset(); } } } } I use 2 concurrent thread (the main thread and one from thread pool) for setting and resetting ManualResetEvents, and try to run test COUNT times, and calculate average execution time. Here is the results (I get it on my dual core notebook with T7250 CPU and Windows 7 x64): ManualResetEvent ManualResetEventSlim Difference is obvious and serious – in 10 times! So, I think preferable way is using ManualResetEventSlim, because not always on calling Set() and Reset() will be called “heavy” methods for working with Windows kernel-mode objects. It’s a small and nice improvement! ;)

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• Steady zoom on center in LWJGL (Modelview)

  - by l5p4ngl312

  I am having a problem in LWJGL with zooming in and out. I am using glScaled(zoom, zoom, 1) before glTranslated. There are 2 problems: 1. The rate of zoom speeds up a lot when zooming out (lower zoom value). 2. It zooms in on the bottom left corner of the screen rather than the center. Eventually, I would like to have the zoom focused on the mouse position. I have tried to fix these problems by make it glScaled(zoom^12, zoom^12, 1) so that the greater the zoom value, the faster it will zoom in order to balance out the faster zoom at lower zoom values. To compensate for the zoom focused on the bottom left, I have tried to subtract (zoom+1)^10 + 2^10 from the X and Y of each sprite. This results in a curved zoom path, first to the left and then to the right. It is a 2D game.

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• Diamond-square terrain generation problem

  - by kafka

  I've implemented a diamond-square algorithm according to this article: http://www.lighthouse3d.com/opengl/terrain/index.php?mpd2 The problem is that I get these steep cliffs all over the map. It happens on the edges, when the terrain is recursively subdivided: Here is the source: void DiamondSquare(unsigned x1,unsigned y1,unsigned x2,unsigned y2,float range) { int c1 = (int)x2 - (int)x1; int c2 = (int)y2 - (int)y1; unsigned hx = (x2 - x1)/2; unsigned hy = (y2 - y1)/2; if((c1 <= 1) || (c2 <= 1)) return; // Diamond stage float a = m_heightmap[x1][y1]; float b = m_heightmap[x2][y1]; float c = m_heightmap[x1][y2]; float d = m_heightmap[x2][y2]; float e = (a+b+c+d) / 4 + GetRnd() * range; m_heightmap[x1 + hx][y1 + hy] = e; // Square stage float f = (a + c + e + e) / 4 + GetRnd() * range; m_heightmap[x1][y1+hy] = f; float g = (a + b + e + e) / 4 + GetRnd() * range; m_heightmap[x1+hx][y1] = g; float h = (b + d + e + e) / 4 + GetRnd() * range; m_heightmap[x2][y1+hy] = h; float i = (c + d + e + e) / 4 + GetRnd() * range; m_heightmap[x1+hx][y2] = i; DiamondSquare(x1, y1, x1+hx, y1+hy, range / 2.0); // Upper left DiamondSquare(x1+hx, y1, x2, y1+hy, range / 2.0); // Upper right DiamondSquare(x1, y1+hy, x1+hx, y2, range / 2.0); // Lower left DiamondSquare(x1+hx, y1+hy, x2, y2, range / 2.0); // Lower right } Parameters: (x1,y1),(x2,y2) - coordinates that define a region on a heightmap (default (0,0)(128,128)). range - basically max. height. (default 32) Help would be greatly appreciated.

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• PHP DL Function

  - by Pete Herbert Penito

  Is allowing dynamic extension loading dangerous for some reason? I ask because I need it to include the pecl oauth.so extension to make the Google Adwords PHP SDK work using dl(). I've tried all other alternatives but just can't get it to work: http://php.net/manual/en/function.dl.php enable_dl is set to off by default inside my php.ini, I enabled it, restarted apache and it works. If it's safe to use why is it disabled by default? I'm the only user with access to the server and it will be hosting a web application. Any advice would be helpful!

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• Loops, Recursion and Memoization in JavaScript

  - by Ken Dason

  Originally posted on: http://geekswithblogs.net/kdason/archive/2013/07/25/loops-recursion-and-memoization-in-javascript.aspxAccording to Wikipedia, the factorial of a positive integer n (denoted by n!) is the product of all positive integers less than or equal to n. For example, 5! = 5 x 4 x 3 x 2 x 1 = 120. The value of 0! is 1. We can use factorials to demonstrate iterative loops and recursive functions in JavaScript.  Here is a function that computes the factorial using a for loop: Output: Time Taken: 51 ms Here is the factorial function coded to be called recursively: Output: Time Taken: 165 ms We can speed up the recursive function with the use of memoization.  Hence,  if the value has previously been computed, it is simply returned and the recursive call ends. Output: Time Taken: 17 ms

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• How to use call web service action in SharePoint2013 workflow

  - by ybbest

  In SharePoint2013, you can use call web service action and loop. In this post, I will show you how to achieve this. 1. Create a List workflow called CallWebService 2. Create a variable called listurl and assign the value to http://sp2010/_vti_bin/listdata.svc 3. Create a dictionary variable called RequestHeaders and add the following key value pairs. 4. Call the web service with the HttpHeaders you just build in the previous step and store the response in the variable ResponseContent. 5. The ResponseContent variable is the Dynamic values (in SharePoint designer it will be called dictionary type) and it is new feature for SharePoint2013 workflow. We can use the following actions to count the number items in the variable. 6. You can use loop in SharePoint 2013 workflow and out each list title as shown below.

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• How to Customize Fonts and Colors for Gnome Panels in Ubuntu Linux

  - by The Geek

  Earlier this week we showed you how to make the Gnome Panels totally transparent, but you really need some customized fonts and colors to make the effect work better. Here’s how to do it. This article is the first part of a multi-part series on how to customize the Ubuntu desktop, written by How-To Geek reader and ubergeek, Omar Hafiz. Changing the Gnome Colors the Easy Way You’ll first need to install Gnome Color Chooser which is available in the default repositories (the package name is gnome-color-chooser). Then go to System > Preferences > Gnome Color Chooser to launch the program. When you see all these tabs you immediately know that Gnome Color Chooser does not only change the font color of the panel, but also the color of the fonts all over Ubuntu, desktop icons, and many other things as well. Now switch to the panel tab, here you can control every thing about your panels. You can change font, font color, background and background color of the panels and start menus. Tick the “Normal” option and choose the color you want for the panel font. If you want you can change the hover color of the buttons on the panel by too. A little below the color option is the font options, this includes the font, font size, and the X and Y positioning of the font. The first two options are pretty straight forward, they change the typeface and the size. The X-Padding and Y-Padding may confuse you but they are interesting, they may give a nice look for your panels by increasing the space between items on your panel like this: X-Padding:   Y-Padding:   The bottom half of the window controls the look of your start menus which is the Applications, Places, and Systems menus. You can customize them just the way you did with the panel.   Alright, this was the easy way to change the font of your panels. Changing the Gnome Theme Colors the Command-Line Way The other hard (not so hard really) way will be changing the configuration files that tell your panel how it should look like. In your Home Folder, press Ctrl+H to show the hidden files, now find the file “.gtkrc-2.0”, open it and insert this line in it. If there are any other lines in the file leave them intact. include “/home/<username>/.gnome2/panel-fontrc” Don’t forget to replace the <user_name> with you user account name. When done close and save the file. Now navigate the folder “.gnome2” from your Home Folder and create a new file and name it “panel-fontrc”. Open the file you just created with a text editor and paste the following in it: style “my_color”{fg[NORMAL] = “#FF0000”}widget “*PanelWidget*” style “my_color”widget “*PanelApplet*” style “my_color” This text will make the font red. If you want other colors you’ll need to replace the Hex value/HTML Notation (in this case #FF0000) with the value of the color you want. To get the hex value you can use GIMP, Gcolor2 witch is available in the default repositories or you can right-click on your panel > Properties > Background tab then click to choose the color you want and copy the Hex value. Don’t change any other thing in the text. When done, save and close. Now press Alt+F2 and enter “killall gnome-panel” to force it to restart or you can log out and login again. Most of you will prefer the first way of changing the font and color for it’s ease of applying and because it gives you much more options but, some may not have the ability/will to download and install a new program on their machine or have reasons of their own for not to using it, that’s why we provided the two way. Latest Features How-To Geek ETC How to Enable User-Specific Wireless Networks in Windows 7 How to Use Google Chrome as Your Default PDF Reader (the Easy Way) How To Remove People and Objects From Photographs In Photoshop Ask How-To Geek: How Can I Monitor My Bandwidth Usage? Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff Here’s a Super Simple Trick to Defeating Fake Anti-Virus Malware The Splendiferous Array of Culinary Tools [Infographic] Add a Real-Time Earth Wallpaper App to Ubuntu with xplanetFX The Citroen GT – An Awesome Video Game Car Brought to Life [Video] Final Man vs. Machine Round of Jeopardy Unfolds; Watson Dominates Give Chromium-Based Browser Desktop Notifications a Native System Look in Ubuntu Chrome Time Track Is a Simple Task Time Tracker

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• C# Adds Optional and Named Arguments

  Earlier this month Microsoft released Visual Studio 2010, the .NET Framework 4.0 (which includes ASP.NET 4.0), and new versions of their core programming languages: C# 4.0 and Visual Basic 10. In designing the latest versions of C# and VB, Microsoft has worked to bring the two languages into closer parity. Certain features available in C# were missing in VB, and vice-a-versa. Last week I wrote about Visual Basic 2010's language enhancements, which include implicit line continuation, auto-implemented properties, and collection initializers - three useful features that were available in previous versions of C#. Similarly, C# 4.0 introduces new features to the C# programming language that were available in earlier versions of Visual Basic, namely optional arguments and named arguments. Optional arguments allow developers to specify default values for one or more arguments to a method. When calling such a method, these optional arguments may be omitted, in which case their default value is used. In a nutshell, optional arguments allow for a more terse syntax for method overloading. Named arguments, on the other hand, improve readability by allowing developers to indicate the name of an argument (along with its value) when calling a method. This article examines how to use optional arguments and named arguments in C# 4.0. Read on to learn more! Read More >Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• C# Adds Optional and Named Arguments

  Earlier this month Microsoft released Visual Studio 2010, the .NET Framework 4.0 (which includes ASP.NET 4.0), and new versions of their core programming languages: C# 4.0 and Visual Basic 10. In designing the latest versions of C# and VB, Microsoft has worked to bring the two languages into closer parity. Certain features available in C# were missing in VB, and vice-a-versa. Last week I wrote about Visual Basic 2010's language enhancements, which include implicit line continuation, auto-implemented properties, and collection initializers - three useful features that were available in previous versions of C#. Similarly, C# 4.0 introduces new features to the C# programming language that were available in earlier versions of Visual Basic, namely optional arguments and named arguments. Optional arguments allow developers to specify default values for one or more arguments to a method. When calling such a method, these optional arguments may be omitted, in which case their default value is used. In a nutshell, optional arguments allow for a more terse syntax for method overloading. Named arguments, on the other hand, improve readability by allowing developers to indicate the name of an argument (along with its value) when calling a method. This article examines how to use optional arguments and named arguments in C# 4.0. Read on to learn more! Read More >

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• Options for EC2 ec2-create-snapshot and family

  - by shabda

  I am trying to use the various tools provided by ec2-ami-tools Eg, ec2-create-snapshot -h .... -K, --private-key KEY Specify KEY as the private key to use. Defaults to the value of the EC2_PRIVATE_KEY environment variable (if set). Overrides the default. -C, --cert CERT Specify CERT as the X509 certificate to use. Defaults to the value of the EC2_CERT environment variable (if set). Overrides the default. -K and -C are two required values, and I cant understand what values are these expecting? If I create a Keypair from Elasticfox, I get only one file to download and a fingerprint. So which of this need to get where?

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• Why enumerator structs are a really bad idea

  - by Simon Cooper

  If you've ever poked around the .NET class libraries in Reflector, I'm sure you would have noticed that the generic collection classes all have implementations of their IEnumerator as a struct rather than a class. As you will see, this design decision has some rather unfortunate side effects... As is generally known in the .NET world, mutable structs are a Very Bad Idea; and there are several other blogs around explaining this (Eric Lippert's blog post explains the problem quite well). In the BCL, the generic collection enumerators are all mutable structs, as they need to keep track of where they are in the collection. This bit me quite hard when I was coding a wrapper around a LinkedList<int>.Enumerator. It boils down to this code: sealed class EnumeratorWrapper : IEnumerator<int> { private readonly LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } The key line here is the MoveNext method. When I initially coded this, I thought that the call to m_Enumerator.MoveNext() would alter the enumerator state in the m_Enumerator class variable and so the enumeration would proceed in an orderly fashion through the collection. However, when I ran this code it went into an infinite loop - the m_Enumerator.MoveNext() call wasn't actually changing the state in the m_Enumerator variable at all, and my code was looping forever on the first collection element. It was only after disassembling that method that I found out what was going on The MoveNext method above results in the following IL: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000, [1] valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator CS$0$0001) L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: stloc.1 L_0008: ldloca.s CS$0$0001 L_000a: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000f: stloc.0 L_0010: br.s L_0012 L_0012: ldloc.0 L_0013: ret } Here, the important line is 0002 - m_Enumerator is accessed using the ldfld operator, which does the following: Finds the value of a field in the object whose reference is currently on the evaluation stack. So, what the MoveNext method is doing is the following: public bool MoveNext() { LinkedList<int>.Enumerator CS$0$0001 = this.m_Enumerator; bool CS$1$0000 = CS$0$0001.MoveNext(); return CS$1$0000; } The enumerator instance being modified by the call to MoveNext is the one stored in the CS$0$0001 variable on the stack, and not the one in the EnumeratorWrapper class instance. Hence why the state of m_Enumerator wasn't getting updated. Hmm, ok. Well, why is it doing this? If you have a read of Eric Lippert's blog post about this issue, you'll notice he quotes a few sections of the C# spec. In particular, 7.5.4: ...if the field is readonly and the reference occurs outside an instance constructor of the class in which the field is declared, then the result is a value, namely the value of the field I in the object referenced by E. And my m_Enumerator field is readonly! Indeed, if I remove the readonly from the class variable then the problem goes away, and the code works as expected. The IL confirms this: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000) L_0000: nop L_0001: ldarg.0 L_0002: ldflda valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000c: stloc.0 L_000d: br.s L_000f L_000f: ldloc.0 L_0010: ret } Notice on line 0002, instead of the ldfld we had before, we've got a ldflda, which does this: Finds the address of a field in the object whose reference is currently on the evaluation stack. Instead of loading the value, we're loading the address of the m_Enumerator field. So now the call to MoveNext modifies the enumerator stored in the class rather than on the stack, and everything works as expected. Previously, I had thought enumerator structs were an odd but interesting feature of the BCL that I had used in the past to do linked list slices. However, effects like this only underline how dangerous mutable structs are, and I'm at a loss to explain why the enumerators were implemented as structs in the first place. (interestingly, the SortedList<TKey, TValue> enumerator is a struct but is private, which makes it even more odd - the only way it can be accessed is as a boxed IEnumerator!). I would love to hear people's theories as to why the enumerators are implemented in such a fashion. And bonus points if you can explain why LinkedList<int>.Enumerator.Reset is an explicit implementation but Dispose is implicit... Note to self: never ever ever code a mutable struct.

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• Unable to use Gmail in Thunderbird 3

  - by Jatin Ganhotra

  Mozilla Thunderbird v.3.1.7 I am trying to setup Gmail, but none of the settings are working. I have tried every resource: Blogs, tutorials Instructions by Google Instructions by Thunderbird Questions here But, still its not working. My settings are as follows Server Settings Server Type: IMAP Mail server Server Name: imap.gmail.com Username: [email protected] Port: 993 Default: 993 Connection Security: SSL/TLS Authentication method: Encrypted password Outgoing server (SMTP) Server Name: smtp.gmail.com Port: 587 Default: 25 Connection Security: STARTTLS Authentication method: Encrypted password Username: [email protected] IMAP is enabled in my Gmail settings. ERROR: Connection to the server [email protected] timed out. I am behind a proxy server and I have configured those settings under: Thunderbird Preferences - Advanced - Network and Disk Space - Connection Settings - Manual Proxy Configuration The proxy configuration works, as when I created a Blogs and News feeds a/c, it was working properly and fetching the feeds for me. So, Thunderbird is configured properly as per the proxy settings. Help me.

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• need some concrete examples on user stories, tasks and how they relate to functional and technical specifications

  - by gideon

  Little heads up, Im the only lonely dev building/planning/mocking my project as I go. Ive come up with a preview release that does only the core aspects of the system, with good business value and I've coded most of the UI as dirty throw-able mockups over nicely abstracted and very minimal base code. In the end I know quite well what my clients want on the whole. I can't take agile-ish cowboying anymore because Im completely dis-organized and have no paper plan and since my clients are happy, things are getting more complex with more features and ideas. So I started using and learning Agile & Scrum Here are my problems: I know what a functional spec is.(sample): Do all user stories and/or scenarios become part of the functional spec? I know what user stories and tasks are. Are these kinda user stories? I dont see any Business Value reason added to them. I made a mind map using freemind, I had problems like this: Actor : Finance Manager Can Add a Financial Plan into the system because well thats the point of it? What Business Value reason do I add for things like this? Example : A user needs to be able to add a blog article (in the blogger app) because..?? Its the point of a blogger app, it centers around that feature? How do I go into the finer details and system definitions: Actor: Finance Manager Action: Adds a finance plan. This adding is a complicated process with lots of steps. What User Story will describe what a finance plan in the system is ?? I can add it into the functional spec under definitions explaining what a finance plan is and how one needs to add it into the system, but how do I get to the backlog planning from there? Example: A Blog Article is mostly a textual document that can be written in rich text in the system. To add a blog article one must...... But how do you create backlog list/features out of this? Where are the user stories for what a blog article is and how one adds/removes it? Finally, I'm a little confused about the relations between functional specs and user stories. Will my spec contain user stories in them with UI mockups? Now will these user stories then branch out tasks which will make up something like a technical specification? Example : EditorUser Can add a blog article. Use XML to store blog article. Add a form to add blog. Add Windows Live Writer Support. That would be agile tasks but would that also be part of/or form the technical specs? Some concrete examples/answers of my questions would be nice!!

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• How to use call web service action in SharePoint2013 workflow

  - by ybbest

  In SharePoint2013, you can use call web service action and loop. In this post, I will show you how to achieve this. 1. Create a List workflow called CallWebService 2. Create a variable called listurl and assign the value to http://sp2010/_vti_bin/listdata.svc 3. Create a dictionary variable called RequestHeaders and add the following key value pairs. 4. Call the web service with the HttpHeaders you just build in the previous step and store the response in the variable ResponseContent. 5. The ResponseContent variable is the Dynamic values (in SharePoint designer it will be called dictionary type) and it is new feature for SharePoint2013 workflow. We can use the following actions to count the number items in the variable. 6. You can use loop in SharePoint 2013 workflow and out each list title as shown below.

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• Extending Currying: Partial Functions in Javascript

  - by kerry

  Last week I posted about function currying in javascript.  This week I am taking it a step further by adding the ability to call partial functions. Suppose we have a graphing application that will pull data via Ajax and perform some calculation to update a graph.  Using a method with the signature ‘updateGraph(id,value)’. To do this, we have do something like this: 1: for(var i=0;i<objects.length;i++) { 2: Ajax.request('/some/data',{id:objects[i].id},function(json) { 3: updateGraph(json.id, json.value); 4: } 5: } This works fine.  But, using this method we need to return the id in the json response from the server.  This works fine, but is not that elegant and increase network traffic. Using partial function currying we can bind the id parameter and add the second parameter later (when returning from the asynchronous call).  To do this, we will need the updated curry method.  I have added support for sending additional parameters at runtime for curried methods. 1: Function.prototype.curry = function(scope) { 2: scope = scope || window 3: var args = []; 4: for (var i=1, len = arguments.length; i < len; ++i) { 5: args.push(arguments[i]); 6: } 7: var m = this; 8: return function() { 9: for (var i=0, len = arguments.length; i < len; ++i) { 10: args.push(arguments[i]); 11: } 12: return m.apply(scope, args); 13: }; 14: } To partially curry this method we will call the curry method with the id parameter, then the request will callback on it with just the value.  Any additional parameters are appended to the method call. 1: for(var i=0;i<objects.length;i++) { 2: var id=objects[i].id; 3: Ajax.request('/some/data',{id: id}, updateGraph.curry(id)); 4: } As you can see, partial currying gives is a very useful tool and this simple method should be a part of every developer’s toolbox.

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• Add Windows 7 to boot menu

  - by Cumatru

  Device Boot Start End Blocks Id System /dev/sda1 * 1 13 102400 7 HPFS/NTFS - system restore /dev/sda2 13 4674 37436416 7 HPFS/NTFS - Windows 7 /dev/sda3 4674 58843 435116032 7 HPFS/NTFS - data storage /dev/sda4 58843 60802 15728640 83 Linux - Ubuntu 10.10 Initially i´ve installed StartUpManager. This ( i think ) added another 4 instances of Linux + memtest to my boot menu list. Altough, i din´t see any boot menu. It boots into Ubuntu after a few seconds. I´ve tried to add windows 7, but i did not succeed. This is a part of my menu.lst file. title Ubuntu 10.10, kernel 2.6.35-24-generic uuid 1c9748e2-2f11-4a6c-91c0-7310d48c4a7a kernel /boot/vmlinuz-2.6.35-24-generic root=UUID=1c9748e2-2f11-4a6c-91c0-7310d48c4a7a ro quiet splash initrd /boot/initrd.img-2.6.35-24-generic title Chainload into GRUB 2 root 1c9748e2-2f11-4a6c-91c0-7310d48c4a7a kernel /boot/grub/core.img title Ubuntu 10.10, memtest86+ uuid 1c9748e2-2f11-4a6c-91c0-7310d48c4a7a kernel /boot/memtest86+.bin menuentry “Windows 7? { set root=(hd0,2) chainloader +1 } And this is after a upgrade-grub Searching for GRUB installation directory ... found: /boot/grub Searching for default file ... found: /boot/grub/default Testing for an existing GRUB menu.lst file ... found: /boot/grub/menu.lst Searching for splash image ... none found, skipping ... Found kernel: /boot/vmlinuz-2.6.35-24-generic Found kernel: /boot/vmlinuz-2.6.35-22-generic Found GRUB 2: /boot/grub/core.img Found kernel: /boot/memtest86+.bin Updating /boot/grub/menu.lst ... done Later Edit: Ive added the following in 40_custom from /etc/grub.d/ and ive decommented hidden menu line from menu.lst, but i still cant see any boot menu. Ive also tried to press ESC and SHIFT. menuentry "Windows 7 (loader) (on /dev/sda1)" { insmod part_msdos insmod ntfs set root='(hd0,msdos1)' chainloader +1 } menuentry "Windows 7 (loader) (on /dev/sda1)" { insmod part_msdos insmod ntfs set root='(hd0,msdos0)' chainloader +1 } menuentry "Windows 7 (loader) (on /dev/sda1)" { set root= hd(0,0) chainloader +1 } menuentry "!Windows 7 (loader) (on /dev/sda1)" { set root= hd(0,1) chainloader +1 } menuentry "!!Windows 7 (loader) (on /dev/sda1)" { set root= hd(0,2) chainloader +1 }

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• Can't add NetworkManager applet to gnome panel

  - by Nate

  I have researched this problem extensively and I can't seem to find an answer. In Ubuntu 10.04 LTS, I want to connect to my VPN through the NetworkManager applet. I installed all the network manager packages, including the gnome client. I understand I need to add the "Notification Area" to the panel, which I have done. I checked that the NetworkManager is running: nate@nate-desktop:~$ service network-manager status network-manager start/running, process 763 In /etc/NetworkManager/nm-system-settings.conf, I have added managed=true (don't know if this matters, but I saw it suggested on one forum): nate@nate-desktop:~$ more /etc/NetworkManager/nm-system-settings.conf # This file is installed into /etc/NetworkManager, and is loaded by # NetworkManager by default. To override, specify: '--config file' # during NM startup. This can be done by appending to DAEMON_OPTS in # the file: # # /etc/default/NetworkManager # [main] plugins=ifupdown,keyfile [ifupdown] #managed=false managed=true I restarted NetworkManager and tried rebooting, too. At this point, it looks like NetworkManager is running but it's not appearing in the NotificationArea of the panel. I don't know what else to try. Any ideas?

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• Advanced reporting in Oracle Service Bus

  - by [email protected]

  v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 21 false false false FR-BE X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tableau Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; 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:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Reporting in OSB is useful, it allows you to audit message going through OSB. The service bus console allows you to view the content that you reported. To report data you simply use the Report action in your proxy. The action itself is rather straightforward. You specify the content to report ($body for example), an optional key for easier search (for example the id of the record) and that's it. Sometimes though, what you want to is a bit more complicated. I recently had a case where the key was built from the message type (XML) and the id of the message. Seems quite simple but the id could be any element anywhere in the message depending on its type. This could be handled by 'if' statement but adding new cases would mean changing the proxy service and if you have lots of message types this can get boring so I wanted the solution to be as dynamic as possible (read "just change a configuration file and that's it"). The following entry details how you can make this dynamic in your proxy by using XQuery/XSLT.   First step the XQuery We're going to use an XQuery to make the mapping between the XML message type and the location of the identifier in it. We assume here that the message type is the first node of the input XML and use a rather simple Xpath to find the identifier.  The XQuery looks like this for two messages : <reportmapping>                 <row>                                <logical>messageType1</logical>                                <type>MT1</type>                                <reportingreferencelocation>//customID</reportingreferencelocation>                 </row>                 <row>                                <logical>messageType2</logical>                                <type>MT2</type>                                <reportingreferencelocation>//theOtherIDLocation</reportingreferencelocation>                 </row>   </reportmapping>   Second step the XSLT To get the identifier value of the dynamic path, we're going to use an XSLT transformation. This XSLT takes an XML parameter as input which contains our xpath (coming from the previous XQuery). The XSLT looks like this : <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xalan="http://xml.apache.org/xalan">               <xsl:param name="PathToNode"/>               <xsl:template match="/">                             <IDVALUE>                                           <xsl:value-of select="xalan:evaluate($PathToNode/reportingreferencelocation)"/>                             </ IDVALUE >               </xsl:template> </xsl:stylesheet> (note the use of a xalan function here. Xalan is the XSLT processor used in weblogic server)   Last step, the proxy service We're now going to wire everything in the proxy service. First we assign the XQuery to a variable. We then get the entry in the XQuery corresponding to the record we're treating. We're then extracting the id of the message using the XSLT transformation Final assign is to built the final variable that will be used as the reporting key. The report action is then called with this variable. Everything is setup. We're now ready to test.   Testing the solution Using the test console, we're sending our first XML ... <messageType1>                 <sender>test console 1</sender>                 <customID>ID12345</customID >                 <content>                                 <field1>value of field 1</field1>                 </content> </messageType1>   ... and a second one of another supported type <messageType2>                 <header>                                 <theOtherIDLocation >ID67890</theOtherIDLocation >                 </header> <body>                                <data>Test data</data>                 </body> </messageType2>   Reporting result is :  Conclusion Report is done as expected. Now if a new message type must be supported we only have to modify the XQuery and nothing at the proxy service level.   Sample project attached to this entry.sbconfig-dynamicReport.jar  

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• C#/XNA get hardware mouse position

  - by Sunder

  I'm using C# and trying to get hardware mouse position. First thing I tryed was simple XNA functionality that is simple to use Vector2 position = new Vector2(Mouse.GetState().X, Mouse.GetState().Y); After that i do the drawing of mouse as well, and comparing to windows hardware mouse, this new mouse with xna provided coordinates is "slacking off". By that i mean, that it is behind by few frames. For example if game is runing at 600 fps, of curse it will be responsive, but at 60 fps software mouse delay is no longer acceptable. Therefore I tried using what I thought was a hardware mouse, [DllImport("user32.dll")] [return: MarshalAs(UnmanagedType.Bool)] public static extern bool GetCursorPos(out POINT lpPoint); but the result was exactly the same. I also tried geting Windows form cursor, and that was a dead end as well - worked, but with the same delay. Messing around with xna functionality: GraphicsDeviceManager.SynchronizeWithVerticalRetrace = true/false Game.IsFixedTimeStep = true/fale did change the delay time for somewhat obvious reasons, but the bottom line is that regardless it still was behind default Windows mouse. I'v seen in some games, that they provide option for hardware acelerated mouse, and in others(I think) it is already by default. Can anyone give some lead on how to achieve that.

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• Informed TDD &ndash; Kata &ldquo;To Roman Numerals&rdquo;

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/05/28/informed-tdd-ndash-kata-ldquoto-roman-numeralsrdquo.aspxIn a comment on my article on what I call Informed TDD (ITDD) reader gustav asked how this approach would apply to the kata “To Roman Numerals”. And whether ITDD wasn´t a violation of TDD´s principle of leaving out “advanced topics like mocks”. I like to respond with this article to his questions. There´s more to say than fits into a commentary. Mocks and TDD I don´t see in how far TDD is avoiding or opposed to mocks. TDD and mocks are orthogonal. TDD is about pocess, mocks are about structure and costs. Maybe by moving forward in tiny red+green+refactor steps less need arises for mocks. But then… if the functionality you need to implement requires “expensive” resource access you can´t avoid using mocks. Because you don´t want to constantly run all your tests against the real resource. True, in ITDD mocks seem to be in almost inflationary use. That´s not what you usually see in TDD demonstrations. However, there´s a reason for that as I tried to explain. I don´t use mocks as proxies for “expensive” resource. Rather they are stand-ins for functionality not yet implemented. They allow me to get a test green on a high level of abstraction. That way I can move forward in a top-down fashion. But if you think of mocks as “advanced” or if you don´t want to use a tool like JustMock, then you don´t need to use mocks. You just need to stand the sight of red tests for a little longer ;-) Let me show you what I mean by that by doing a kata. ITDD for “To Roman Numerals” gustav asked for the kata “To Roman Numerals”. I won´t explain the requirements again. You can find descriptions and TDD demonstrations all over the internet, like this one from Corey Haines. Now here is, how I would do this kata differently. 1. Analyse A demonstration of TDD should never skip the analysis phase. It should be made explicit. The requirements should be formalized and acceptance test cases should be compiled. “Formalization” in this case to me means describing the API of the required functionality. “[D]esign a program to work with Roman numerals” like written in this “requirement document” is not enough to start software development. Coding should only begin, if the interface between the “system under development” and its context is clear. If this interface is not readily recognizable from the requirements, it has to be developed first. Exploration of interface alternatives might be in order. It might be necessary to show several interface mock-ups to the customer – even if that´s you fellow developer. Designing the interface is a task of it´s own. It should not be mixed with implementing the required functionality behind the interface. Unfortunately, though, this happens quite often in TDD demonstrations. TDD is used to explore the API and implement it at the same time. To me that´s a violation of the Single Responsibility Principle (SRP) which not only should hold for software functional units but also for tasks or activities. In the case of this kata the API fortunately is obvious. Just one function is needed: string ToRoman(int arabic). And it lives in a class ArabicRomanConversions. Now what about acceptance test cases? There are hardly any stated in the kata descriptions. Roman numerals are explained, but no specific test cases from the point of view of a customer. So I just “invent” some acceptance test cases by picking roman numerals from a wikipedia article. They are supposed to be just “typical examples” without special meaning. Given the acceptance test cases I then try to develop an understanding of the problem domain. I´ll spare you that. The domain is trivial and is explain in almost all kata descriptions. How roman numerals are built is not difficult to understand. What´s more difficult, though, might be to find an efficient solution to convert into them automatically. 2. Solve The usual TDD demonstration skips a solution finding phase. Like the interface exploration it´s mixed in with the implementation. But I don´t think this is how it should be done. I even think this is not how it really works for the people demonstrating TDD. They´re simplifying their true software development process because they want to show a streamlined TDD process. I doubt this is helping anybody. Before you code you better have a plan what to code. This does not mean you have to do “Big Design Up-Front”. It just means: Have a clear picture of the logical solution in your head before you start to build a physical solution (code). Evidently such a solution can only be as good as your understanding of the problem. If that´s limited your solution will be limited, too. Fortunately, in the case of this kata your understanding does not need to be limited. Thus the logical solution does not need to be limited or preliminary or tentative. That does not mean you need to know every line of code in advance. It just means you know the rough structure of your implementation beforehand. Because it should mirror the process described by the logical or conceptual solution. Here´s my solution approach: The arabic “encoding” of numbers represents them as an ordered set of powers of 10. Each digit is a factor to multiply a power of ten with. The “encoding” 123 is the short form for a set like this: {1*10^2, 2*10^1, 3*10^0}. And the number is the sum of the set members. The roman “encoding” is different. There is no base (like 10 for arabic numbers), there are just digits of different value, and they have to be written in descending order. The “encoding” XVI is short for [10, 5, 1]. And the number is still the sum of the members of this list. The roman “encoding” thus is simpler than the arabic. Each “digit” can be taken at face value. No multiplication with a base required. But what about IV which looks like a contradiction to the above rule? It is not – if you accept roman “digits” not to be limited to be single characters only. Usually I, V, X, L, C, D, M are viewed as “digits”, and IV, IX etc. are viewed as nuisances preventing a simple solution. All looks different, though, once IV, IX etc. are taken as “digits”. Then MCMLIV is just a sum: M+CM+L+IV which is 1000+900+50+4. Whereas before it would have been understood as M-C+M+L-I+V – which is more difficult because here some “digits” get subtracted. Here´s the list of roman “digits” with their values: {1, I}, {4, IV}, {5, V}, {9, IX}, {10, X}, {40, XL}, {50, L}, {90, XC}, {100, C}, {400, CD}, {500, D}, {900, CM}, {1000, M} Since I take IV, IX etc. as “digits” translating an arabic number becomes trivial. I just need to find the values of the roman “digits” making up the number, e.g. 1954 is made up of 1000, 900, 50, and 4. I call those “digits” factors. If I move from the highest factor (M=1000) to the lowest (I=1) then translation is a two phase process: Find all the factors Translate the factors found Compile the roman representation Translation is just a look-up. Finding, though, needs some calculation: Find the highest remaining factor fitting in the value Remember and subtract it from the value Repeat with remaining value and remaining factors Please note: This is just an algorithm. It´s not code, even though it might be close. Being so close to code in my solution approach is due to the triviality of the problem. In more realistic examples the conceptual solution would be on a higher level of abstraction. With this solution in hand I finally can do what TDD advocates: find and prioritize test cases. As I can see from the small process description above, there are two aspects to test: Test the translation Test the compilation Test finding the factors Testing the translation primarily means to check if the map of factors and digits is comprehensive. That´s simple, even though it might be tedious. Testing the compilation is trivial. Testing factor finding, though, is a tad more complicated. I can think of several steps: First check, if an arabic number equal to a factor is processed correctly (e.g. 1000=M). Then check if an arabic number consisting of two consecutive factors (e.g. 1900=[M,CM]) is processed correctly. Then check, if a number consisting of the same factor twice is processed correctly (e.g. 2000=[M,M]). Finally check, if an arabic number consisting of non-consecutive factors (e.g. 1400=[M,CD]) is processed correctly. I feel I can start an implementation now. If something becomes more complicated than expected I can slow down and repeat this process. 3. Implement First I write a test for the acceptance test cases. It´s red because there´s no implementation even of the API. That´s in conformance with “TDD lore”, I´d say: Next I implement the API: The acceptance test now is formally correct, but still red of course. This will not change even now that I zoom in. Because my goal is not to most quickly satisfy these tests, but to implement my solution in a stepwise manner. That I do by “faking” it: I just “assume” three functions to represent the transformation process of my solution: My hypothesis is that those three functions in conjunction produce correct results on the API-level. I just have to implement them correctly. That´s what I´m trying now – one by one. I start with a simple “detail function”: Translate(). And I start with all the test cases in the obvious equivalence partition: As you can see I dare to test a private method. Yes. That´s a white box test. But as you´ll see it won´t make my tests brittle. It serves a purpose right here and now: it lets me focus on getting one aspect of my solution right. Here´s the implementation to satisfy the test: It´s as simple as possible. Right how TDD wants me to do it: KISS. Now for the second equivalence partition: translating multiple factors. (It´a pattern: if you need to do something repeatedly separate the tests for doing it once and doing it multiple times.) In this partition I just need a single test case, I guess. Stepping up from a single translation to multiple translations is no rocket science: Usually I would have implemented the final code right away. Splitting it in two steps is just for “educational purposes” here. How small your implementation steps are is a matter of your programming competency. Some “see” the final code right away before their mental eye – others need to work their way towards it. Having two tests I find more important. Now for the next low hanging fruit: compilation. It´s even simpler than translation. A single test is enough, I guess. And normally I would not even have bothered to write that one, because the implementation is so simple. I don´t need to test .NET framework functionality. But again: if it serves the educational purpose… Finally the most complicated part of the solution: finding the factors. There are several equivalence partitions. But still I decide to write just a single test, since the structure of the test data is the same for all partitions: Again, I´m faking the implementation first: I focus on just the first test case. No looping yet. Faking lets me stay on a high level of abstraction. I can write down the implementation of the solution without bothering myself with details of how to actually accomplish the feat. That´s left for a drill down with a test of the fake function: There are two main equivalence partitions, I guess: either the first factor is appropriate or some next. The implementation seems easy. Both test cases are green. (Of course this only works on the premise that there´s always a matching factor. Which is the case since the smallest factor is 1.) And the first of the equivalence partitions on the higher level also is satisfied: Great, I can move on. Now for more than a single factor: Interestingly not just one test becomes green now, but all of them. Great! You might say, then I must have done not the simplest thing possible. And I would reply: I don´t care. I did the most obvious thing. But I also find this loop very simple. Even simpler than a recursion of which I had thought briefly during the problem solving phase. And by the way: Also the acceptance tests went green: Mission accomplished. At least functionality wise. Now I´ve to tidy up things a bit. TDD calls for refactoring. Not uch refactoring is needed, because I wrote the code in top-down fashion. I faked it until I made it. I endured red tests on higher levels while lower levels weren´t perfected yet. But this way I saved myself from refactoring tediousness. At the end, though, some refactoring is required. But maybe in a different way than you would expect. That´s why I rather call it “cleanup”. First I remove duplication. There are two places where factors are defined: in Translate() and in Find_factors(). So I factor the map out into a class constant. Which leads to a small conversion in Find_factors(): And now for the big cleanup: I remove all tests of private methods. They are scaffolding tests to me. They only have temporary value. They are brittle. Only acceptance tests need to remain. However, I carry over the single “digit” tests from Translate() to the acceptance test. I find them valuable to keep, since the other acceptance tests only exercise a subset of all roman “digits”. This then is my final test class: And this is the final production code: Test coverage as reported by NCrunch is 100%: Reflexion Is this the smallest possible code base for this kata? Sure not. You´ll find more concise solutions on the internet. But LOC are of relatively little concern – as long as I can understand the code quickly. So called “elegant” code, however, often is not easy to understand. The same goes for KISS code – especially if left unrefactored, as it is often the case. That´s why I progressed from requirements to final code the way I did. I first understood and solved the problem on a conceptual level. Then I implemented it top down according to my design. I also could have implemented it bottom-up, since I knew some bottom of the solution. That´s the leaves of the functional decomposition tree. Where things became fuzzy, since the design did not cover any more details as with Find_factors(), I repeated the process in the small, so to speak: fake some top level, endure red high level tests, while first solving a simpler problem. Using scaffolding tests (to be thrown away at the end) brought two advantages: Encapsulation of the implementation details was not compromised. Naturally private methods could stay private. I did not need to make them internal or public just to be able to test them. I was able to write focused tests for small aspects of the solution. No need to test everything through the solution root, the API. The bottom line thus for me is: Informed TDD produces cleaner code in a systematic way. It conforms to core principles of programming: Single Responsibility Principle and/or Separation of Concerns. Distinct roles in development – being a researcher, being an engineer, being a craftsman – are represented as different phases. First find what, what there is. Then devise a solution. Then code the solution, manifest the solution in code. Writing tests first is a good practice. But it should not be taken dogmatic. And above all it should not be overloaded with purposes. And finally: moving from top to bottom through a design produces refactored code right away. Clean code thus almost is inevitable – and not left to a refactoring step at the end which is skipped often for different reasons.   PS: Yes, I have done this kata several times. But that has only an impact on the time needed for phases 1 and 2. I won´t skip them because of that. And there are no shortcuts during implementation because of that.

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• How to handle lookup data in a C# ASP.Net MVC4 application?

  - by Jim

  I am writing an MVC4 application to track documents we have on file for our clients. I'm using code first, and have created models for my objects (Company, Document, etc...). I am now faced with the topic of document expiration. Business logic dictates certain documents will expire a set number of days past the document date. For example, Document A might expire in 180 days, Document 2 in 365 days, etc... I have a class for my documents as shown below (simplified for this example). What is the best way for me to create a lookup for expiration values? I want to specify documents of type DocumentA expire in 30 days, type DocumentB expire in 75 days, etc... I can think of a few ways to do this: Lookup table in the database I can query New property in my class (DaysValidFor) which has a custom getter that returns different values based on the DocumentType A method that takes in the document type and returns the number of days and I'm sure there are other ways I'm not even thinking of. My main concern is a) not violating any best practices and b) maintainability. Are there any pros/cons I need to be aware of for the above options, or is this a case of "just pick one and run with it"? One last thought, right now the number of days is a value that does not need to be stored anywhere on a per-document basis -- however, it is possible that business logic will change this (i.e., DocumentA's are 30 days expiration by default, but this DocumentA associated with Company XYZ will be 60 days because we like them). In that case, is a property in the Document class the best way to go, seeing as I need to add that field to the DB? namespace Models { // Types of documents to track public enum DocumentType { DocumentA, DocumentB, DocumentC // etc... } // Document model public class Document { public int DocumentID { get; set; } // Foreign key to companies public int CompanyID { get; set; } public DocumentType DocumentType { get; set; } // Helper to translate enum's value to an integer for DB storage [Column("DocumentType")] public int DocumentTypeInt { get { return (int)this.DocumentType; } set { this.DocumentType = (DocumentType)value; } } [DataType(DataType.Date)] [DisplayFormat(DataFormatString = "{0:MM-dd-yyyy}", ApplyFormatInEditMode = true)] public DateTime DocumentDate { get; set; } // Navigation properties public virtual Company Company { get; set; } } }

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• What is the best file system and allocation size for a USB flash drive?

  - by e-t172

  I'm considering using my 4 GB Kingston DataTraveler USB stick to store my Firefox and Thunderbird profiles for my laptop and desktop PCs. I want to maximize performance when using Firefox. The question is: what is the best file system and allocation size for the fastest Firefox profile operation on a USB flash drive? I'm using Windows 7 on both machines and I don't care about compatibility or the drive's lifetime. I just want to maximize performance. I could even use ext2 with the Ext2 IFS driver if that means it'll be faster. I'm assuming (perhaps I'm wrong) that putting a Firefox profile on a USB stick would be a "lots of small files" usage. In that case, it seems that NTFS would perform best, but I'm not sure. Besides I found nothing regarding the best allocation size to use. Considering that the default allocation size is designed for hard drives (which have different characteristics), I'm assuming that the default allocation size is not the best.

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