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• Podcast interview with Michael Kane

  - by mhornick

  In this podcast interview with Michael Kane, Data Scientist and Associate Researcher at Yale University, Michael discusses the R statistical programming language, computational challenges associated with big data, and two projects involving data analysis he conducted on the stock market "flash crash" of May 6, 2010, and the tracking of transportation routes bird flu H5N1. Michael also worked with Oracle on Oracle R Enterprise, a component of the Advanced Analytics option to Oracle Database Enterprise Edition. In the closing segment of the interview, Michael comments on the relationship between the data analyst and the database administrator and how Oracle R Enterprise provides secure data management, transparent access to data, and improved performance to facilitate this relationship. Listen now...

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• How to understand the memory usage and load average in linux server

  - by Tim

  Hi, I am using a linux server which has 128GB of memory and 24 cores. I use top to see how much it is used. Its output is pasted at the end of the post. Here are two questions: (1) I see that each of the running processes occupies a very small percentage of memory (%MEM no more than 0.2%, and most just 0.0%), but how the total memory is almost used as in the fourth line of output ("Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers")? The sum of used percentage of memory over all processes seems unlikely to achieve almost 100%, doesn't it? (2) how to understand the load average on the first line ("load average: 14.04, 14.02, 14.00")? Thanks and regards! Edit: Thanks! I also really like to hear some rough numbers based on used percentage of memory to determine if a server is heavily loaded, since I once became the one who cramed the server without understanding the current load. Is swap regarded as almost the same as memory? For example, when memory and swap are almost of same size, if the memory is almost running out but the swap is still largely free, may I just view it as if the used percentage of memory + swap is still not high and run other new processes? How would you consider together CPU or memory (or memory + swap) usage? Do you become worried if either of them reaches too high or both? Output of top: $ top top - 12:45:33 up 19 days, 23:11, 18 users, load average: 14.04, 14.02, 14.00 Tasks: 484 total, 12 running, 472 sleeping, 0 stopped, 0 zombie Cpu(s): 36.7%us, 19.7%sy, 0.0%ni, 43.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers Swap: 63111312k total, 500556k used, 62610756k free, 124437752k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 6529 sanchez 18 -2 1075m 219m 13m S 100 0.2 13760:23 MATLAB 13210 timothy 18 -2 48336 37m 1216 R 100 0.0 3:56.75 absurdity 13888 timothy 18 -2 48336 37m 1204 R 100 0.0 2:04.89 absurdity 14542 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.34 absurdity 14544 timothy 18 -2 2888 2076 400 R 100 0.0 1:06.14 gatherData 6183 sanchez 18 -2 1133m 195m 13m S 100 0.2 13676:04 MATLAB 6795 sanchez 18 -2 1079m 210m 13m S 100 0.2 13734:26 MATLAB 10178 timothy 18 -2 48336 37m 1204 R 100 0.0 11:33.93 absurdity 12438 timothy 18 -2 48336 37m 1216 R 100 0.0 5:38.17 absurdity 13661 timothy 18 -2 48336 37m 1216 R 100 0.0 2:44.13 absurdity 14098 timothy 18 -2 48336 37m 1204 R 100 0.0 1:58.31 absurdity 14335 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.93 absurdity 14765 timothy 18 -2 48336 37m 1196 R 99 0.0 0:32.57 absurdity 13445 timothy 18 -2 48336 37m 1216 R 99 0.0 3:01.37 absurdity 28990 root 20 0 0 0 0 S 2 0.0 65:50.21 pdflush 12141 tim 18 -2 19380 1660 1024 R 1 0.0 0:04.04 top 1240 root 15 -5 0 0 0 S 0 0.0 16:07.11 kjournald 9019 root 20 0 296m 4460 2616 S 0 0.0 82:19.51 kdm_greet 1 root 20 0 4028 728 592 S 0 0.0 0:03.11 init 2 root 15 -5 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root RT -5 0 0 0 S 0 0.0 0:01.01 migration/0 4 root 15 -5 0 0 0 S 0 0.0 0:08.13 ksoftirqd/0 5 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT -5 0 0 0 S 0 0.0 17:27.31 migration/1 7 root 15 -5 0 0 0 S 0 0.0 0:01.21 ksoftirqd/1 8 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/1 9 root RT -5 0 0 0 S 0 0.0 10:02.56 migration/2 10 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/2 11 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/2 12 root RT -5 0 0 0 S 0 0.0 4:29.53 migration/3 13 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/3

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• How to stop Thunar being default file browser

  - by Charles Kane

  On a relatively new 11.04 installation Thunar has become the default file browser simply by using it! Whilst I can open Nautilus easily enough, I'd rather it remained as the default, especially when I choose to view files in dual pane. The only action that I can pinpoint that might have given over my files and folders to Thunar is making Nautilus into Nautilus-Elementary (oh and Unity carked it so I reverted rather unwillingly to Classic, glad I did it is so much more stable and this is my production machine and Unity acts as if it is early alpha as far as I can tell!)

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• Reasons Programmers Leave

  - by Kane

  I am interested in finding out why programmers leave their jobs and if the reasons for leaving have resurfaced in your now job? Is the reason for leaving simply down to remuneration, location, I hate my boss / coworker, lack of recognition or retirement / new career path. Update: I am responsible for a team of programmers and testers and I would like to better understand what could motivate my team to leave, and hopefully try to address such issues.

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• Add title to meta analysis forest plot

  - by Timothy Alston

  I am meta-analysing some studies and drawing a forest plot for my results. However I can`t seem to get the forest plot to display the title. An example of my code is: require(meta) parameter1<-metaprop(sm="PLOGIT", event=c(4,16,3,2,10,1,0,2), n=c(90,402,89,29,153,86,21,48), level = 0.95, studlab=c("study 1", "study 2", "study 3", "study 4", "study 5", "study 6", "study 7", "study 8"), title="meta analysis 1") forest(parameter1) When it produces the forest plot, the title "meta analysis 1" is missing. How can I add this in? Thanks in advance, Timothy

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• 11.10 update manager upgrade to 12.04 fails

  - by Kane

  Currently using 11.10 on a new dell vostro 2420 laptop and wanted to upgrade to 12.04.01lte. Using the update manager and clicking the upgrade option first came up with a 'failure to authenticate' message and after a restart of the computer I click the upgrade and it will download 2 files then the popup closes and no further prompts/screens come up. Is there some issue with my laptop that will prevent an upgrade? Or should I just wait and try the upgrade again another day?

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• structure problem in Relational DBMS creation

  - by Kane

  For learning and understanding purpose, I currently want to try to make a small relational DBMS with simple features like (for now) only sequential reading/writing and CREATE TABLE, INSERT, SELECT, UPDATE and DELETE management. I am currently on the "think" part of the project and I am stuck on the way to store the read data in memory. First I was thinking of putting them properly on a structure, but the problem is that tables are all different, know the type of each column is not an issue, but I am not sure C provide a way to make fully dynamic structure. My second and current idea is to make a simple char array of the required length and just get the data by order with cast. But I am not sure if it is the good way to do that part, so I wanted to ask for your opinion and advices about that. Thanks in advance for your help. nb: I hope my question is enough clear and understandable, I still lack of pratice in english

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• Why is Google Webmaster Tools crawling invalid URLS and showing 500 errors?

  - by Amos Kane

  Google Webmaster tools is reporting 12k+ 500 errors. Eeek! None of the URLS are valid- they all contain www.youtube.com. First, why is Google crawling these URLS if they don't exist? I supplied a sitemap, and they are of course not in the sitemap. I don't have a robots.txt blocking anything. I've checked for invalid redirects--none, and checked for unclosed tags or something that would throw www.youtube.com into the URL by accident--none. In every 'linked from', the referring URL is also a bad URL, with www.youtube.com in it. The Google Tools report no malware, and I can't check the server logs because the host won't give me access. Really stuck!! Any ideas appreciated!

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• Dell Vostro 2420 upgrade to 12.04.1 no wifi

  - by Kane

  I have installed 12.04 on a dell vostro 2420 (previously 11.10) and wifi is gone now but wired network remains. I've reviewed the other questions and tried some stuff but no luck yet. The following is the process so far so hopefully someone can help: After installing 12.04 using the additional drivers utility did not bring up any proprietary drivers and using synaptic on installation then reinstallation of bcmwl-kernel-source and b43-fwcutter does not help bring up any drivers either (tried rebooting after as well) I have made sure in the bios that the wlan is turned on, and it appears the laptop does not have a wireless hardware switch, only the keyboard function shortcut which turns bluetooth on and off on the taskbar but there is no lightup of the wireless function on the laptop itself. Dell does not appear to have any drivers for ubuntu and google does not appear to be much help :( Thanks in advance!

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• Is there ever a reason to do all an object's work in a constructor?

  - by Kane

  Let me preface this by saying this is not my code nor my coworkers' code. Years ago when our company was smaller, we had some projects we needed done that we did not have the capacity for, so they were outsourced. Now, I have nothing against outsourcing or contractors in general, but the codebase they produced is a mass of WTFs. That being said, it does (mostly) work, so I suppose it's in the top 10% of outsourced projects I've seen. As our company has grown, we've tried to take more of our development in house. This particular project landed in my lap so I've been going over it, cleaning it up, adding tests, etc etc. There's one pattern I see repeated a lot and it seems so mindblowingly awful that I wondered if maybe there is a reason and I just don't see it. The pattern is an object with no public methods or members, just a public constructor that does all the work of the object. For example, (the code is in Java, if that matters, but I hope this to be a more general question): public class Foo { private int bar; private String baz; public Foo(File f) { execute(f); } private void execute(File f) { // FTP the file to some hardcoded location, // or parse the file and commit to the database, or whatever } } If you're wondering, this type of code is often called in the following manner: for(File f : someListOfFiles) { new Foo(f); } Now, I was taught long ago that instantiated objects in a loop is generally a bad idea, and that constructors should do a minimum of work. Looking at this code it looks like it would be better to drop the constructor and make execute a public static method. I did ask the contractor why it was done this way, and the response I got was "We can change it if you want". Which was not really helpful. Anyway, is there ever a reason to do something like this, in any programming language, or is this just another submission to the Daily WTF?

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• My Website title changes by itself in Google

  - by Kane

  I am doing seo on my friends site www.svipl.in each page has its own metas it did change to new ones then somehow google is taking company name as the meta title I just googled this topic and last few days other people getting same problem , I had similar issue in the past on my own site that soon changed after changing the metas again any seo experts with same problem please help , there is no h1 heading on the company name or alt tag with that also.

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• Network programming under windows: is WSA functions can be more complete than pSock functions [on hold]

  - by Kane

  I plan to make a set of classic socket functions to simplify their usages. Since i work under windows and linux indifferently i usually make it portable (it's not my first version of this set of functions), but i want to do something different this time and dedicate one version to windows, and one other to linux. With that i wonder for the windows version, if the WSA* functions can have any interest using them instead of the psock ones. I have found nothing about a comparison between them, so if any of you have any idea, suggestion, link or benchmark ?

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• Cutting objects and applying texture to cut. Unity3d/C#

  - by Timothy Williams

  Basically what I'm trying to do is figure out how to calculate realtime cutting of objects, and apply a texture to the cut. I found some good scripts, but most of them have been abandoned and aren't really fully working yet. Applying textures: http://forum.unity3d.com/threads/75949-Mesh-Real-Cutting?highlight=mesh+real+cutting Cutting: http://forum.unity3d.com/threads/78594-Object-Cutter Another (Free) Cutter (Also, I'm not entirely sure how this one will handle cutting complex meshes): http://forum.unity3d.com/threads/69992-fake-slicer?p=449114&viewfull=1#post449114 My plan as of right now is to combine links 1 & 2 or 1 & 3 programming wise. What I'm asking here for is any advice on how to advance (links to asset store packages, or other codes to show how to accomplish something complex like this.)

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• How do I blend 2 lightmaps for day/night cycle in Unity?

  - by Timothy Williams

  Before I say anything else: I'm using dual lightmaps, meaning I need to blend both a near and a far. So I've been working on this for a while now, I have a whole day/night cycle set up for renderers and lighting, and everything is working fine and not process intensive. The only problem I'm having is figuring out how I could blend two lightmaps together, I've figured out how to switch lightmaps, but the problem is that looks kind of abrupt and interrupts the experience. I've done hours of research on this, tried all kinds of shaders, pixel by pixel blending, and everything else to no real avail. Pixel by pixel blending in C# turned out to be a bit process intensive for my liking, though I'm still working on cleaning it up and making it run more smoothly. Shaders looked promising, but I couldn't find a shader that could properly blend two lightmaps. Does anyone have any leads on how I could accomplish this? I just need some sort of smooth transition between my daytime and nighttime lightmap. Perhaps I could overlay the two textures and use an alpha channel? Or something like that?

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• Export a .FBX file in Unity3D at runtime

  - by Timothy Williams

  What I'm looking to do is be able to export an object as a .FBX at runtime in Unity3D. I've made a C# script which can export a mesh filter or skinned mesh renderer to a .OBJ file at runtime, but .OBJ doesn't support the same kind of animations and skins that .FBX does. I've been researching this for a while, as of right now it looks like somehow using the Autodesk FBX SDK or some other external .dll would be my best option. Does anyone know of external .dlls I could use for this? Or how to make calls to Autodesk's FBX SDK at runtime? Another option could possibly be to write the mesh information as a text file then convert to .FBX on exporting. Just looking for fellow programmer's thoughts, or tips, or to see if this has been accomplished already. As far as I can tell there isn't any pre-existing scripts to export FBX at runtime in Unity.

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• Creating natural environments that can run on lower end computers in Unity3D/C#

  - by Timothy Williams

  So, I'm starting work on a project soon that will require me to create realistic environments that can preferably run on PC's besides high quality ones. The goal is to get as real an environment as possible while still being easy(ish) to run. The only problem is I've NEVER done anything with 3D environments, making trees sway, grass move, lighting, etc. Can anyone give me any help? Perhaps describe how it's done? Link me to articles? I'm just looking to be pointed in the right direction, not for you to write the code for me. Any help at all would be greatly appreciated, I'm using Unity3D and C# as my language. Thanks, Tim.

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• How do I import service references to Unity3D?

  - by Timothy Williams

  I'm attempting access a service reference in Unity. I need two: the SOAP framework and a separate service called ContentVault. The respective service URL's are: SOAP: http://api.microsofttranslator.com/V2/Soap.svc ContentVault: http://ioun.wizards.com/ContentVault.svc Both services import fine in to Visual Studio. I've tried everything I can think of but they won't work with Unity. I just get various errors (changing depending on which solution I'm trying out). I've attempted using svcutil to export the services as external scripts, but all I got was a bunch of using errors. I've tried converting the code to work with .NET 2.0 to no avail, I've even tried making the services in to .DLL's to no success. How could get these services working with Unity?

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• Getting a sphere to roll down a .FBX object Unity3D/C#

  - by Timothy Williams

  I'm working on a little ramp and ball game in Unity, I modeled the ramp outside Unity and exported it to a .FBX file, then I imported the ramp in to Unity. I set up the ball and ramp, both have Rigidbodies, Ramp is set to isKinematic = true, yet when I play the game the ball just falls right through the ramp and hits the floor below it fine. So it's something wrong with the ramp. Am I doing something wrong? Are .FBX files unable to apply physics? Thanks, Tim.

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• ~/.bashrc return can only 'return' from a function or sourced script

  - by Timothy

  I am trying to setup a OpenStack box to have a look at OpenStack Object Storage (Swift). Looking through the web I found this link; http://swift.openstack.org/development_saio.html#loopback-section I followed the instructions line by line but stuck on step 7 in the "Getting the code and setting up test environment" section. When I execute ~/.bashrc I get; line 6: return: can only 'return' from a function or sourced script. Below is the Line 6 extract from ~/.bashrc. My first reaction is to comment this line out, but I dont know what it does. Can anyone help? #If not running interactively, dont't do anything [ -z "$PS1" ] && return I'm running Ubuntu 12.04 as a VM on Hyper-v if knowing that is useful.

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• C4C - 2012

  - by Timothy Wright

  C4C, in Kansas City, is always a fun event. At points it gets to be a pressure cooker as you zone in trying to crank out some fantastic code in just a few hours, but it is always fun. A great challenge of your skill as a software developer and for a good cause. This year my team helped The United Cerebral Palsy of Greater Kansas City organization to add online job applications and a database for tracking internal training. I keep finding that there is one key rule to pulling off a successful C4C weekend project, and that is “Keep It Simple”. Each time you want to add that one cool little feature you have to ask yourself.. Is it really necessary? and Do I have time for that? And if you are going to learn something new you should ask yourself if you’re really going to be able to learn that AND finish the project in the given time. Sometimes the less elegant code is the better code if it works. That said… You get a great amount of freedom to build the solution the way you want. Typically, the software we build for the charities will save them a lot of money and time and make their jobs easier. You are able to build the software you know you are capable of creating from your own ideas. I highly recommend any developers in the area to signup next year and show off your skills. I know I will!

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• Finding shortest path on a hexagonal grid

  - by Timothy Mayes

  I'm writing a turn based game that has some simulation elements. One task i'm hung up on currently is with path finding. What I want to do is, each turn, move an ai adventurer one tile closer to his target using his current x,y and his target x,y. In trying to figure this out myself I can determine 4 directions no problem by using dx = currentX - targetY dy = currentY - targetY but I'm not sure how to determine which of the 6 directions is actually the "best" or "shortest" route. For example the way its setup currently I use East, West, NE, NW, SE, SW but to get to the NE tile i move East then NW instead of just moving NW. I hope this wasn't all rambling. Even just a link or two to get me started would be nice. Most of the info i've found is on drawing the grids and groking the wierd coordinate system needed. Thanks in advance Tim

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• Testing Workflows &ndash; Test-After

  - by Timothy Klenke

  Originally posted on: http://geekswithblogs.net/TimothyK/archive/2014/05/30/testing-workflows-ndash-test-after.aspxIn this post I’m going to outline a few common methods that can be used to increase the coverage of of your test suite.  This won’t be yet another post on why you should be doing testing; there are plenty of those types of posts already out there.  Assuming you know you should be testing, then comes the problem of how do I actual fit that into my day job.  When the opportunity to automate testing comes do you take it, or do you even recognize it? There are a lot of ways (workflows) to go about creating automated tests, just like there are many workflows to writing a program.  When writing a program you can do it from a top-down approach where you write the main skeleton of the algorithm and call out to dummy stub functions, or a bottom-up approach where the low level functionality is fully implement before it is quickly wired together at the end.  Both approaches are perfectly valid under certain contexts. Each approach you are skilled at applying is another tool in your tool belt.  The more vectors of attack you have on a problem – the better.  So here is a short, incomplete list of some of the workflows that can be applied to increasing the amount of automation in your testing and level of quality in general.  Think of each workflow as an opportunity that is available for you to take. Test workflows basically fall into 2 categories:  test first or test after.  Test first is the best approach.  However, this post isn’t about the one and only best approach.  I want to focus more on the lesser known, less ideal approaches that still provide an opportunity for adding tests.  In this post I’ll enumerate some test-after workflows.  In my next post I’ll cover test-first. Bug Reporting When someone calls you up or forwards you a email with a vague description of a bug its usually standard procedure to create or verify a reproduction plan for the bug via manual testing and log that in a bug tracking system.  This can be problematic.  Often reproduction plans when written down might skip a step that seemed obvious to the tester at the time or they might be missing some crucial environment setting. Instead of data entry into a bug tracking system, try opening up the test project and adding a failing unit test to prove the bug.  The test project guarantees that all aspects of the environment are setup properly and no steps are missing.  The language in the test project is much more precise than the English that goes into a bug tracking system. This workflow can easily be extended for Enhancement Requests as well as Bug Reporting. Exploratory Testing Exploratory testing comes in when you aren’t sure how the system will behave in a new scenario.  The scenario wasn’t planned for in the initial system requirements and there isn’t an existing test for it.  By definition the system behaviour is “undefined”. So write a new unit test to define that behaviour.  Add assertions to the tests to confirm your assumptions.  The new test becomes part of the living system specification that is kept up to date with the test suite. Examples This workflow is especially good when developing APIs.  When you are finally done your production API then comes the job of writing documentation on how to consume the API.  Good documentation will also include code examples.  Don’t let these code examples merely exist in some accompanying manual; implement them in a test suite. Example tests and documentation do not have to be created after the production API is complete.  It is best to write the example code (tests) as you go just before the production code. Smoke Tests Every system has a typical use case.  This represents the basic, core functionality of the system.  If this fails after an upgrade the end users will be hosed and they will be scratching their heads as to how it could be possible that an update got released with this core functionality broken. The tests for this core functionality are referred to as “smoke tests”.  It is a good idea to have them automated and run with each build in order to avoid extreme embarrassment and angry customers. Coverage Analysis Code coverage analysis is a tool that reports how much of the production code base is exercised by the test suite.  In Visual Studio this can be found under the Test main menu item. The tool will report a total number for the code coverage, which can be anywhere between 0 and 100%.  Coverage Analysis shouldn’t be used strictly for numbers reporting.  Companies shouldn’t set minimum coverage targets that mandate that all projects must have at least 80% or 100% test coverage.  These arbitrary requirements just invite gaming of the coverage analysis, which makes the numbers useless. The analysis tool will break down the coverage by the various classes and methods in projects.  Instead of focusing on the total number, drill down into this view and see which classes have high or low coverage.  It you are surprised by a low number on a class this is an opportunity to add tests. When drilling through the classes there will be generally two types of reaction to a surprising low test coverage number.  The first reaction type is a recognition that there is low hanging fruit to be picked.  There may be some classes or methods that aren’t being tested, which could easy be.  The other reaction type is “OMG”.  This were you find a critical piece of code that isn’t under test.  In both cases, go and add the missing tests. Test Refactoring The general theme of this post up to this point has been how to add more and more tests to a test suite.  I’ll step back from that a bit and remind that every line of code is a liability.  Each line of code has to be read and maintained, which costs money.  This is true regardless whether the code is production code or test code. Remember that the primary goal of the test suite is that it be easy to read so that people can easily determine the specifications of the system.  Make sure that adding more and more tests doesn’t interfere with this primary goal. Perform code reviews on the test suite as often as on production code.  Hold the test code up to the same high readability standards as the production code.  If the tests are hard to read then change them.  Look to remove duplication.  Duplicate setup code between two or more test methods that can be moved to a shared function.  Entire test methods can be removed if it is found that the scenario it tests is covered by other tests.  Its OK to delete a test that isn’t pulling its own weight anymore. Remember to only start refactoring when all the test are green.  Don’t refactor the tests and the production code at the same time.  An automated test suite can be thought of as a double entry book keeping system.  The unchanging, passing production code serves as the tests for the test suite while refactoring the tests. As with all refactoring, it is best to fit this into your regular work rather than asking for time later to get it done.  Fit this into the standard red-green-refactor cycle.  The refactor step no only applies to production code but also the tests, but not at the same time.  Perhaps the cycle should be called red-green-refactor production-refactor tests (not quite as catchy).   That about covers most of the test-after workflows I can think of.  In my next post I’ll get into test-first workflows.

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• How to make a ball fall faster on a ramp? Unity3D/C#

  - by Timothy Williams

  So, I'm making a ball game. Where you pick up the ball, drop it on a ramp, and it flies off in to blocks. The only problem right now is it falls at a normal speed, then lightly falls off, not nearly fast enough to get over the wall and hit the blocks. Is there any way to make the ball go faster down the ramp? Maybe even make it go faster depending on what height you dropped it from (e.g. if you hold it way above the ramp, and drop it, it will drop faster than if you dropped it right above the ramp.) Thanks.

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• DRY and SRP

  - by Timothy Klenke

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

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• How to make a ball fall faster on a ramp?

  - by Timothy Williams

  So, I'm making a ball game. Where you pick up the ball, drop it on a ramp, and it flies off in to blocks. The only problem right now is it falls at a normal speed, then lightly falls off, not nearly fast enough to get over the wall and hit the blocks. Is there any way to make the ball go faster down the ramp? Maybe even make it go faster depending on what height you dropped it from (e.g. if you hold it way above the ramp, and drop it, it will drop faster than if you dropped it right above the ramp.)

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