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• What is the kd tree intersection logic?

  - by bobobobo

  I'm trying to figure out how to implement a KD tree. On page 322 of "Real time collision detection" by Ericson The text section is included below in case Google book preview doesn't let you see it the time you click the link text section Relevant section: The basic idea behind intersecting a ray or directed line segment with a k-d tree is straightforward. The line is intersected against the node's splitting plane, and the t value of intersection is computed. If t is within the interval of the line, 0 <= t <= tmax, the line straddles the plane and both children of the tree are recursively descended. If not, only the side containing the segment origin is recursively visited. So here's what I have: (open image in new tab if you can't see the lettering) The logical tree Here the orange ray is going thru the 3d scene. The x's represent intersection with a plane. From the LEFT, the ray hits: The front face of the scene's enclosing cube, The (1) splitting plane The (2.2) splitting plane The right side of the scene's enclosing cube But here's what would happen, naively following Ericson's basic description above: Test against splitting plane (1). Ray hits splitting plane (1), so left and right children of splitting plane (1) are included in next test. Test against splitting plane (2.1). Ray actually hits that plane, (way off to the right) so both children are included in next level of tests. (This is counter-intuitive - shouldn't only the bottom node be included in subsequent tests) Can some one describe what happens when the orange ray goes through the scene correctly?

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• Boost your infrastructure with Coherence into the Cloud

  - by Nino Guarnacci

  Authors: Nino Guarnacci & Francesco Scarano,  at this URL could be found the original article:  http://blogs.oracle.com/slc/coherence_into_the_cloud_boost. Thinking about the enterprise cloud, come to mind many possible configurations and new opportunities in enterprise environments. Various customers needs that serve as guides to this new trend are often very different, but almost always united by two main objectives: Elasticity of infrastructure both Hardware and Software Investments related to the progressive needs of the current infrastructure Characteristics of innovation and economy. A concrete use case that I worked on recently demanded the fulfillment of two basic requirements of economy and innovation.The client had the need to manage a variety of data cache, which can process complex queries and parallel computational operations, maintaining the caches in a consistent state on different server instances, on which the application was installed.In addition, the customer was looking for a solution that would allow him to manage the likely situations in load peak during certain times of the year.For this reason, the customer requires a replication site, on which convey part of the requests during periods of peak; the desire was, however, to prevent the immobilization of investments in owned hardware-software architectures; so, to respond to this need, it was requested to seek a solution based on Cloud technologies and architectures already offered by the market. Coherence can already now address the requirements of large cache between different nodes in the cluster, providing further technology to search and parallel computing, with the simultaneous use of all hardware infrastructure resources. Moreover, thanks to the functionality of "Push Replication", which can replicate and update the information contained in the cache, even to a site hosted in the cloud, it is satisfied the need to make resilient infrastructure that can be based also on nodes temporarily housed in the Cloud architectures. There are different types of configurations that can be realized using the functionality "Push-Replication" of Coherence. Configurations can be either: Active - Passive  Hub and Spoke Active - Active Multi Master Centralized Replication Whereas the architecture of this particular project consists of two sites (Site 1 and Site Cloud), between which only Site 1 is enabled to write into the cache, it was decided to adopt an Active-Passive Configuration type (Hub and Spoke). If, however, the requirement should change over time, it will be particularly easy to change this configuration in an Active-Active configuration type. Although very simple, the small sample in this post, inspired by the specific project is effective, to better understand the features and capabilities of Coherence and its configurations. Let's create two distinct coherence cluster, located at miles apart, on two different domain contexts, one of them "hosted" at home (on-premise) and the other one hosted by any cloud provider on the network (or just the same laptop to test it :)). These two clusters, which we call Site 1 and Site Cloud, will contain the necessary information, so a simple client can insert data only into the Site 1. On both sites will be subscribed a listener, who listens to the variations of specific objects within the various caches. To implement these features, you need 4 simple classes: CachedResponse.java Represents the POJO class that will be inserted into the cache, and fulfills the task of containing useful information about the hypothetical links navigation ResponseSimulatorHelper.java Represents a link simulator, which has the task of randomly creating objects of type CachedResponse that will be added into the caches CacheCommands.java Represents the model of our example, because it is responsible for receiving instructions from the controller and performing basic operations against the cache, such as insert, delete, update, listening, objects within the cache Shell.java It is our controller, which give commands to be executed within the cache of the two Sites So, summarily, we execute the java class "Shell", asking it to put into the cache 100 objects of type "CachedResponse" through the java class "CacheCommands", then the simulator "ResponseSimulatorHelper" will randomly create new instances of objects "CachedResponse ". Finally, the Shell class will listen to for events occurring within the cache on the Site Cloud, while insertions and deletions are performed on Site 1. Now, we realize the two configurations of two respective sites / cluster: Site 1 and Site Cloud.For the Site 1 we define a cache of type "distributed" with features of "read and write", using the cache class store for the "push replication", a functionality offered by the project "incubator" of Oracle Coherence.For the "Site Cloud" we expect even the definition of “distributed” cache type with tcp proxy feature enabled, so it can receive updates from Site 1.  Coherence Cache Config XML file for "storage node" on "Site 1" site1-prod-cache-config.xml Coherence Cache Config XML file for "storage node" on "Site Cloud" site2-prod-cache-config.xml For two clients "Shell" which will connect respectively to the two clusters we have provided two easy access configurations.  Coherence Cache Config XML file for Shell on "Site 1" site1-shell-prod-cache-config.xml Coherence Cache Config XML file for Shell on "Site Cloud" site2-shell-prod-cache-config.xml Now, we just have to get everything and run our tests. To start at least one "storage" node (which holds the data) for the "Cloud Site", we can run the standard class  provided OOTB by Oracle Coherence com.tangosol.net.DefaultCacheServer with the following parameters and values:-Xmx128m-Xms64m-Dcom.sun.management.jmxremote -Dtangosol.coherence.management=all -Dtangosol.coherence.management.remote=true -Dtangosol.coherence.distributed.localstorage=true -Dtangosol.coherence.cacheconfig=config/site2-prod-cache-config.xml-Dtangosol.coherence.clusterport=9002-Dtangosol.coherence.site=SiteCloud To start at least one "storage" node (which holds the data) for the "Site 1", we can perform again the standard class provided by Coherence  com.tangosol.net.DefaultCacheServer with the following parameters and values:-Xmx128m-Xms64m-Dcom.sun.management.jmxremote -Dtangosol.coherence.management=all -Dtangosol.coherence.management.remote=true -Dtangosol.coherence.distributed.localstorage=true -Dtangosol.coherence.cacheconfig=config/site1-prod-cache-config.xml-Dtangosol.coherence.clusterport=9001-Dtangosol.coherence.site=Site1 Then, we start the first client "Shell" for the "Cloud Site", launching the java class it.javac.Shell  using these parameters and values: -Xmx64m-Xms64m-Dcom.sun.management.jmxremote -Dtangosol.coherence.management=all -Dtangosol.coherence.management.remote=true -Dtangosol.coherence.distributed.localstorage=false -Dtangosol.coherence.cacheconfig=config/site2-shell-prod-cache-config.xml-Dtangosol.coherence.clusterport=9002-Dtangosol.coherence.site=SiteCloud Finally, we start the second client "Shell" for the "Site 1", re-launching a new instance of class  it.javac.Shell  using  the following parameters and values: -Xmx64m-Xms64m-Dcom.sun.management.jmxremote -Dtangosol.coherence.management=all -Dtangosol.coherence.management.remote=true -Dtangosol.coherence.distributed.localstorage=false -Dtangosol.coherence.cacheconfig=config/site1-shell-prod-cache-config.xml-Dtangosol.coherence.clusterport=9001-Dtangosol.coherence.site=Site1  And now, let’s execute some tests to validate and better understand our configuration. TEST 1The purpose of this test is to load the objects into the "Site 1" cache and seeing how many objects are cached on the "Site Cloud". Within the "Shell" launched with parameters to access the "Site 1", let’s write and run the command: load test/100 Within the "Shell" launched with parameters to access the "Site Cloud" let’s write and run the command: size passive-cache Expected result If all is OK, the first "Shell" has uploaded 100 objects into a cache named "test"; consequently the "push-replication" functionality has updated the "Site Cloud" by sending the 100 objects to the second cluster where they will have been posted into a respective cache, which we named "passive-cache". TEST 2The purpose of this test is to listen to deleting and adding events happening on the "Site 1" and that are replicated within the cache on "Cloud Site". In the "Shell" launched with parameters to access the "Site Cloud" let’s write and run the command: listen passive-cache/name like '%' or a "cohql" query, with your preferred parameters In the "Shell" launched with parameters to access the "Site 1" let’s write and run the following commands: load test/10 load test2/20 delete test/50 Expected result If all is OK, the "Shell" to Site Cloud let us to listen to all the add and delete events within the cache "cache-passive", whose objects satisfy the query condition "name like '%' " (ie, every objects in the cache; you could change the tests and create different queries).Through the Shell to "Site 1" we launched the commands to add and to delete objects on different caches (test and test2). With the "Shell" running on "Site Cloud" we got the evidence (displayed or printed, or in a log file) that its cache has been filled with events and related objects generated by commands executed from the" Shell "on" Site 1 ", thanks to "push-replication" feature.  Other tests can be performed, such as, for example, the subscription to the events on the "Site 1" too, using different "cohql" queries, changing the cache configuration,  to effectively demonstrate both the potentiality and  the versatility produced by these different configurations, even in the cloud, as in our case. More information on how to configure Coherence "Push Replication" can be found in the Oracle Coherence Incubator project documentation at the following link: http://coherence.oracle.com/display/INC10/Home More information on Oracle Coherence "In Memory Data Grid" can be found at the following link: http://www.oracle.com/technetwork/middleware/coherence/overview/index.html To download and execute the whole sources and configurations of the example explained in the above post,  click here to download them; After download the last available version of the Push-Replication Pattern library implementation from the Oracle Coherence Incubator site, and download also the related and required version of Oracle Coherence. For simplicity the required .jarS to execute the example (that can be found into the Push-Replication-Pattern  download and Coherence Distribution download) are: activemq-core-5.3.1.jar activemq-protobuf-1.0.jar aopalliance-1.0.jar coherence-commandpattern-2.8.4.32329.jar coherence-common-2.2.0.32329.jar coherence-eventdistributionpattern-1.2.0.32329.jar coherence-functorpattern-1.5.4.32329.jar coherence-messagingpattern-2.8.4.32329.jar coherence-processingpattern-1.4.4.32329.jar coherence-pushreplicationpattern-4.0.4.32329.jar coherence-rest.jar coherence.jar commons-logging-1.1.jar commons-logging-api-1.1.jar commons-net-2.0.jar geronimo-j2ee-management_1.0_spec-1.0.jar geronimo-jms_1.1_spec-1.1.1.jar http.jar jackson-all-1.8.1.jar je.jar jersey-core-1.8.jar jersey-json-1.8.jar jersey-server-1.8.jar jl1.0.jar kahadb-5.3.1.jar miglayout-3.6.3.jar org.osgi.core-4.1.0.jar spring-beans-2.5.6.jar spring-context-2.5.6.jar spring-core-2.5.6.jar spring-osgi-core-1.2.1.jar spring-osgi-io-1.2.1.jar At this URL could be found the original article: http://blogs.oracle.com/slc/coherence_into_the_cloud_boost Authors: Nino Guarnacci & Francesco Scarano

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• Choosing the right language for the job

  - by Ampt

  I'm currently working for a company on the engineering team of about 5-6 people and have been given the job of heading up the redesign of an embedded system tester. We've decided the general requirements and attributes that would be desirable in the system, and now I have to decide on a language to use for the system, or at the very least come up with a list of languages with pros and cons to present to the team. The general idea of the project is that we currently have a tester written in c++, which was never designed to be a tester, but instead has evolved to be such over the course of 3-4 years due to need. Writing tests for a new product requires modifying the 'framework' and writing code that is completely non-human readable or intuitive due to the way the system was originally designed. Now, we've decided that the time to modify this tester for each new product that we want to test has become too high and want to partially re-write the system so that we can program the actual tests in a scripting language that would then use the modified c++ framework on the back end to test the actual systems. The c++ framework would be responsible for doing all the actual work and the scripting language would just integrate with that to tell the framework what to do. Never having programmed in a scripting language (we program embedded systems), I've run into a wall where I have no experience with any of the languages that we could possibly use, but must somehow give pros and cons of each language so that we can choose the best one for the job. Currently my short list of possibilities includes: Python TCL Lua Perl My question is this: How can a person evaluate a language that he/she has never used before? What criteria are good indicators for a languages potential usability on a project? While helpful suggestions for my particular case are appreciated, I feel that this is a good skill to possess and would like to be able to apply this to many different projects if at all possible

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• How can I move a polygon edge 1 unit away from the center?

  - by Stephen

  Let's say I have a polygon class that is represented by a list of vector classes as vertices, like so: var Vector = function(x, y) { this.x = x; this.y = y; }, Polygon = function(vectors) { this.vertices = vectors; }; Now I make a polygon (in this case, a square) like so: var poly = new Polygon([ new Vector(2, 2), new Vector(5, 2), new Vector(5, 5), new Vector(2, 5) ]); So, the top edge would be [poly.vertices[0], poly.vertices[1]]. I need to stretch this polygon by moving each edge away from the center of the polygon by one unit, along that edge's normal. The following example shows the first edge, the top, moved one unit up: The final polygon should look like this new one: var finalPoly = new Polygon([ new Vector(1, 1), new Vector(6, 1), new Vector(6, 6), new Vector(1, 6) ]); It is important that I iterate, moving one edge at a time, because I will be doing some collision tests after moving each edge. Here is what I tried so far (simplified for clarity), which fails triumphantly: for(var i = 0; i < vertices.length; i++) { var a = vertices[i], b = vertices[i + 1] || vertices[0]; // in case of final vertex var ax = a.x, ay = a.y, bx = b.x, by = b.y; // get some new perpendicular vectors var a2 = new Vector(-ay, ax), b2 = new Vector(-by, bx); // make into unit vectors a2.convertToUnitVector(); b2.convertToUnitVector(); // add the new vectors to the original ones a.add(a2); b.add(b2); // the rest of the code, collision tests, etc. } This makes my polygon start slowly rotating and sliding to the left, instead of what I need. Finally, the example shows a square, but the polygons in question could be anything. They will always be convex, and always with vertices in clockwise order.

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• White Paper on Analysis Services Tabular Large-scale Solution #ssas #tabular

  - by Marco Russo (SQLBI)

  Since the first beta of Analysis Services 2012, I worked with many companies designing and implementing solutions based on Analysis Services Tabular. I am glad that Microsoft published a white paper about a case-study using one of these scenarios: An Analysis Services Case Study: Using Tabular Models in a Large-scale Commercial Solution. Alberto Ferrari is the author of the white paper and many people contributed to it. The final result is a very technical document based on a case study, which provides a level of detail that I don’t see often in other case studies (which are usually more marketing-oriented). This white paper has the following structure: Requirements (data model, capacity planning, client tool) Options considered (SQL Server Columnstore Indexes, SSAS Multidimensional, SSAS Tabular) Data Model optimizations (memory compression, query performance, scalability) Partitioning and Processing strategy for near real-time latency Hardware selection (NUMA analysis, Azure VM tests) Scalability tests (estimation of maximum users per node) If you are in charge of evaluating Tabular as analytical engine, or if you have to design your solution based on Tabular, this white paper is a must read. But if you just want to increase your knowledge of Analysis Services, you will find a lot of useful technical information. That said, my favorite quote of the document is the following one, funny but true: […] After several trials, the clear winner was a video gaming machine that one guy on the team used at home. That computer outperformed any available server, running twice as fast as the server-class machines we had in house. At that point, it was clear that the criteria for choosing the server would have to be expanded a bit, simply because it would have been impossible to convince the boss to build a cluster of gaming machines and trust it to serve our customers.  But, honestly, if a business has the flexibility to buy gaming machines (assuming the machines can handle capacity) – do this. Owen Graupman, inContact I want to write a longer discussion about how companies are adopting Tabular in scenarios where it is the hidden engine of a more complex solution (and not the classical “BI system”), because it is more frequent than you might expect (and has several advantages over many alternative approaches).

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• Best method to organize/manage dependencies in the VCS within a large solution

  - by SnOrfus

  A simple scenario: 2 projects are in version control The application The test(s) A significant number of checkins are made to the application daily. CI builds and runs all of the automation nightly. In order to write and/or run tests you need to have built the application (to reference/load instrumented assemblies). Now, consider the application to be massive, such that building it is prohibitive in time (an entire day to compile). The obvious side effect here, is that once you've performed a build locally, it is immediately inconsistent with latest. For instance: If I were to sync with latest, and open up one of the test projects, it would not locally build until I built the application. This is the same when syncing to another branch/build/tag. So, in order to even start working, I need to wait a day to build the application locally, so that the assemblies could be loaded - and then those assemblies wouldn't be latest. How do you organize the repository or (ideally) your development environment such that you can continually develop tests against whatever the current build is, or a given specific build, while minimizing building the application as much as possible?

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• Understanding branching strategy/workflow correctly

  - by burnersk

  I'm using svn without branches (trunk-only) for a very long time at my workplace. I had discovered most or all of the issues related to projects which do not have any branching strategy. Unlikely this is not going to change at my workplace but for my private projects. For my private projects which most includes coworkers and working together at the same time on different features I like to have an robust branching strategy with supports long-term releases powered by git. I find out that the Atlassian Toolchain (JIRA, Stash and Bamboo) helped me most and it also recommending me an branching strategy which I like to verify for the team needs. The branching strategy was taken directly from Atlassian Stash recommendation with a small modification to the hotfix branch tree. All hotfixes should also merged into mainline. The branching strategy in words mainline (also known as master with git or trunk with svn) contains the "state of the art" developing release. Everything here was successfully checked with various automated tests (through Bamboo) and looks like everything is working. It is not proven as working because of possible missing tests. It is ready to use but not recommended for production. feature covers all new features which are not completely finished. Once a feature is finished it will be merged into mainline. Sample branch: feature/ISSUE-2-A-nice-Feature bugfix fixes non-critical bugs which can wait for the next normal release. Sample branch: bugfix/ISSUE-1-Some-typos production owns the latest release. hotfix fixes critical bugs which have to be release urgent to mainline, production and all affected long-term *release*es. Sample branch: hotfix/ISSUE-3-Check-your-math release is for long-term maintenance. Sample branches: release/1.0, release/1.1 release/1.0-rc1 I am not an expert so please provide me feedback. Which problems might appear? Which parts are missing or slowing down the productivity?

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• Code Contracts and Pex at MSDN Live 2010

  - by terje

  One of the 6 sessions I and Mikael Nitell is running on MSDN Live 2010 here in Norway is about Code Quality, and part of that session goes through the use of Code Contracts and Pex.  Both fantastic tools ! They can be used togethers, but are also completely independent from each other, and can be used as a single Code Contracts  has to downloaded separately from VS 2010 (works also on VS 2008).   Start looking at http://msdn.microsoft.com/en-us/devlabs/dd491992.aspx . This download is a free download.   Code Contracts originates form the ideas of Bertrand Meyer – Design by Contract, take a look here. Pex is found on the MSDN Subscription download, so it requires an active MSDN Subscription. Start to get it from here http://research.microsoft.com/en-us/projects/pex/downloads.aspx .  The current version as of 14.4.10 is 0.9, which works with the 2010 RC.  A new version is due this week.  Pex is a tool to generate unit tests, and does this very intelligently.  Perfect to make tests for legacy code, but also to make sure you get all paths tested.  See the Reference information and project startup information.

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• Is it useful to unit test methods where the only logic is guards?

  - by Vaccano

  Say I have a method like this: public void OrderNewWidget(Widget widget) { if ((widget.PartNumber > 0) && (widget.PartAvailable)) { WigdetOrderingService.OrderNewWidgetAsync(widget.PartNumber); } } I have several such methods in my code (the front half to an async Web Service call). I am debating if it is useful to get them covered with unit tests. Yes there is logic here, but it is only guard logic. (Meaning I make sure I have the stuff I need before I allow the web service call to happen.) Part of me says "sure you can unit test them, but it is not worth the time" (I am on a project that is already behind schedule). But the other side of me says, if you don't unit test them, and someone changes the Guards, then there could be problems. But the first part of me says back, if someone changes the guards, then you are just making more work for them (because now they have to change the guards and the unit tests for the guards). For example, if my service assumes responsibility to check for Widget availability then I may not want that guard any more. If it is under unit test, I have to change two places now. I see pros and cons in both ways. So I thought I would ask what others have done.

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• Should one generally develop a client library for REST services to help prevent API breakages?

  - by BestPractices

  We have a project where UI code will be developed by the same team but in a different language (Python/Django) from the services layer (REST/Java). The code for each layer exits in different code repositories and which can follow different release cycles. I'm trying to come up with a process that will prevent/reduce breaking changes in the services layer from the perspective of the UI layer. I've thought to write integration tests at the UI layer level that we'll run whenever we build the UI or the services layer (we're using Jenkins as our CI tool to build the code which is in two Git repos) and if there are failures then something in the services layer broke and the commit is not accepted. Would it also be a good idea (is it a best practice?) to have the developer of the services layer create and maintain a client library for the REST service that exists in the UI layer that they will update whenever there is a breaking change in their Service API? Conceivably, we would then have the advantage of a statically-typed API that the UI code builds against. If the client library API changes, then the UI code won't compile (so we'll know sooner that there was a breaking change). I'd also still run the integration tests upon building the UI or services layer to further validate that the integration between UI and the service(s) still works.

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• How relevant are Brainbench scores when evaluating candidates?

  - by Newtopian

  I've seen many companies using certification services such as Brainbench when evaluating candidates. Most times they use it as a secondary screen prior to interview or as a validation to choose between candidates. What is your experience with Brainbench scores? Did you try the tests yourself, and if so do you feel the score is meaningful enough to be used as part of a hiring process? Difficult choice. Consensus seems to be that BB cert are not very good as a certification. The biggest argument was around the fact that some of the questions are too precise to form a good evaluation. this view can probably be tempered somewhat but still, to hold someone's future solely on the results of this evaluation would be irresponsible. That said, I still think it is possible to use them properly to gain additional objective knowledge on a candidate's level of expertise provided the test is done in a controlled environment ensuring that all taking it stand on equal footing. Thus I went with the answer that best reflected this view keeping in mind that it is still just an hour long 50ish multiple choice question to evaluate skills and knowledge that take years to acquire. To be taken with a grain of salt ! In short, The tests have value but weather or not they are worth the money is another debate. Thanks all for your time.

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• How can I justify software testing to management?

  - by Nate

  I work for a small company (less than 200 employees) whose software group only makes up a small part of our staff (4 employees, occasionally with a few contractors). The four of us have been making strides in transitioning to better practices, and one of the next logical steps is to improve our testing. As anyone who has done any meaningful tests knows, testing takes a lot of time - and at my company, it takes too much time to justify to management, so we generally do what little we do on the sly. I don't think this is serving us well, as we keep coming up against otherwise avoidable problems when we ship under-tested software. I would like to be able to come to management with a justification for hiring a dedicated software test engineer (someone who can both write automated tests and perform manual ones). Are there any good published studies that show the benefits of adding such a position to a small company? Where can I find information about costs associated with the position? I plan on doing a little number crunching on our own history, but having some external sources to point to would help bolster my case.

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• What does your Lisp workflow look like?

  - by Duncan Bayne

  I'm learning Lisp at the moment, coming from a language progression that is Locomotive BASIC - Z80 Assembler - Pascal - C - Perl - C# - Ruby. My approach is to simultaneously: write a simple web-scraper using SBCL, QuickLisp, closure-html, and drakma watch the SICP lectures I think this is working well; I'm developing good 'Lisp goggles', in that I can now read Lisp reasonably easily. I'm also getting a feel for how the Lisp ecosystem works, e.g. Quicklisp for dependencies. What I'm really missing, though, is a sense of how a seasoned Lisper actually works. When I'm coding for .NET, I have Visual Studio set up with ReSharper and VisualSVN. I write tests, I implement, I refactor, I commit. Then when I'm done enough of that to complete a story, I write some AUATs. Then I kick off a Release build on TeamCity to push the new functionality out to the customer for testing & hopefully approval. If it's an app that needs an installer, I use either WiX or InnoSetup, obviously building the installer through the CI system. So, my question is: as an experienced Lisper, what does your workflow look like? Do you work mostly in the REPL, or in the editor? How do you do unit tests? Continuous integration? Packaging & deployment? When you sit down at your desk, steaming mug of coffee to one side and a framed photo of John McCarthy to the other, what is it that you do? Currently, I feel like I am getting to grips with Lisp coding, but not Lisp development ...

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• How to analyze a scenario where a bug didn't get caught and adjust development workflow to prevent similar errors

  - by durron597

  I had a bug that was really difficult to track down, because all the unit tests were green, but the production application didn't work properly. Here's what happened: I had a filter class that set my application to ignore data that was not in some specified time windows. The unit test, which seemed thorough to me, turned green. Additionally, my integration tests also produced results as expected. Production, however, did not work. As a result of the first two bullets, this problem was very difficult to find. It turned out the problem was that my test dates were using my time zone (America/Chicago) but the production data was providing dates in UTC, which I did not realize, and the logic for the filter wasn't correct for UTC dates. (I was using joda time DateTime objects). Where did my workflow break down? Did I fail to produce a spec that specified that the logic needed to handle dates in any time zone? Did I fail to thoroughly consider all cases at the unit test level? Did I fail to insure the integration test was sufficiently similar to production? Other? What changes can I make to my workflow to better prevent this sort of mistake in the future? How can I more effectively debug a problem when there is an issue in production but not in testing?

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• How Mature is Your Database Change Management Process?

  - by Ben Rees

  .dbd-banner p{ font-size:0.75em; padding:0 0 10px; margin:0 } .dbd-banner p span{ color:#675C6D; } .dbd-banner p:last-child{ padding:0; } @media ALL and (max-width:640px){ .dbd-banner{ background:#f0f0f0; padding:5px; color:#333; margin-top: 5px; } } -- Database Delivery Patterns & Practices Further Reading Organization and team processes How do you get your database schema changes live, on to your production system? As your team of developers and DBAs are working on the changes to the database to support your business-critical applications, how do these updates wend their way through from dev environments, possibly to QA, hopefully through pre-production and eventually to production in a controlled, reliable and repeatable way? In this article, I describe a model we use to try and understand the different stages that customers go through as their database change management processes mature, from the very basic and manual, through to advanced continuous delivery practices. I also provide a simple chart that will help you determine “How mature is our database change management process?” This process of managing changes to the database – which all of us who have worked in application/database development have had to deal with in one form or another – is sometimes known as Database Change Management (even if we’ve never used the term ourselves). And it’s a difficult process, often painfully so. Some developers take the approach of “I’ve no idea how my changes get live – I just write the stored procedures and add columns to the tables. It’s someone else’s problem to get this stuff live. I think we’ve got a DBA somewhere who deals with it – I don’t know, I’ve never met him/her”. I know I used to work that way. I worked that way because I assumed that making the updates to production was a trivial task – how hard can it be? Pause the application for half an hour in the middle of the night, copy over the changes to the app and the database, and switch it back on again? Voila! But somehow it never seemed that easy. And it certainly was never that easy for database changes. Why? Because you can’t just overwrite the old database with the new version. Databases have a state – more specifically 4Tb of critical data built up over the last 12 years of running your business, and if your quick hotfix happened to accidentally delete that 4Tb of data, then you’re “Looking for a new role” pretty quickly after the failed release. There are a lot of other reasons why a managed database change management process is important for organisations, besides job security, not least: Frequency of releases. Many business managers are feeling the pressure to get functionality out to their users sooner, quicker and more reliably. The new book (which I highly recommend) Lean Enterprise by Jez Humble, Barry O’Reilly and Joanne Molesky provides a great discussion on how many enterprises are having to move towards a leaner, more frequent release cycle to maintain their competitive advantage. It’s no longer acceptable to release once per year, leaving your customers waiting all year for changes they desperately need (and expect) Auditing and compliance. SOX, HIPAA and other compliance frameworks have demanded that companies implement proper processes for managing changes to their databases, whether managing schema changes, making sure that the data itself is being looked after correctly or other mechanisms that provide an audit trail of changes. We’ve found, at Red Gate that we have a very wide range of customers using every possible form of database change management imaginable. Everything from “Nothing – I just fix the schema on production from my laptop when things go wrong, and write it down in my notebook” to “A full Continuous Delivery process – any change made by a dev gets checked in and recorded, fully tested (including performance tests) before a (tested) release is made available to our Release Management system, ready for live deployment!”. And everything in between of course. Because of the vast number of customers using so many different approaches we found ourselves struggling to keep on top of what everyone was doing – struggling to identify patterns in customers’ behavior. This is useful for us, because we want to try and fit the products we have to different needs – different products are relevant to different customers and we waste everyone’s time (most notably, our customers’) if we’re suggesting products that aren’t appropriate for them. If someone visited a sports store, looking to embark on a new fitness program, and the store assistant suggested the latest $10,000 multi-gym, complete with multiple weights mechanisms, dumb-bells, pull-up bars and so on, then he’s likely to lose that customer. All he needed was a pair of running shoes! To solve this issue – in an attempt to simplify how we understand our customers and our offerings – we built a model. This is a an attempt at trying to classify our customers in to some sort of model or “Customer Maturity Framework” as we rather grandly term it, which somehow simplifies our understanding of what our customers are doing. The great statistician, George Box (amongst other things, the “Box” in the Box-Jenkins time series model) gave us the famous quote: “Essentially all models are wrong, but some are useful” We’ve taken this quote to heart – we know it’s a gross over-simplification of the real world of how users work with complex legacy and new database developments. Almost nobody precisely fits in to one of our categories. But we hope it’s useful and interesting. There are actually a number of similar models that exist for more general application delivery. We’ve found these from ThoughtWorks/Forrester, from InfoQ and others, and initially we tried just taking these models and replacing the word “application” for “database”. However, we hit a problem. From talking to our customers we know that users are far less further down the road of mature database change management than they are for application development. As a simple example, no application developer, who wants to keep his/her job would develop an application for an organisation without source controlling that code. Sure, he/she might not be using an advanced Gitflow branching methodology but they’ll certainly be making sure their code gets managed in a repo somewhere with all the benefits of history, auditing and so on. But this certainly isn’t the case (yet) for the database – a very large segment of the people we speak to have no source control set up for their databases whatsoever, even at the most basic level (for example, keeping change scripts in a source control system somewhere). By the way, if this is you, Red Gate has a great whitepaper here, on the barriers people face getting a source control process implemented at their organisations. This difference in maturity is the same as you move in to areas such as continuous integration (common amongst app developers, relatively rare for database developers) and automated release management (growing amongst app developers, very rare for the database). So, when we created the model we started from scratch and biased the levels of maturity towards what we actually see amongst our customers. But, what are these stages? And what level are you? The table below describes our definitions for four levels of maturity – Baseline, Beginner, Intermediate and Advanced. As I say, this is a model – you won’t fit any of these categories perfectly, but hopefully one will ring true more than others. We’ve also created a PDF with a flow chart to help you find which of these groups most closely matches your team:  Download the Database Delivery Maturity Framework PDF here   Level D1 – Baseline Work directly on live databases Sometimes work directly in production Generate manual scripts for releases. Sometimes use a product like SQL Compare or similar to do this Any tests that we might have are run manually Level D2 – Beginner Have some ad-hoc DB version control such as manually adding upgrade scripts to a version control system Attempt is made to keep production in sync with development environments There is some documentation and planning of manual deployments Some basic automated DB testing in process Level D3 – Intermediate The database is fully version-controlled with a product like Red Gate SQL Source Control or SSDT Database environments are managed Production environment schema is reproducible from the source control system There are some automated tests Have looked at using migration scripts for difficult database refactoring cases Level D4 – Advanced Using continuous integration for database changes Build, testing and deployment of DB changes carried out through a proper database release process Fully automated tests Production system is monitored for fast feedback to developers   Does this model reflect your team at all? Where are you on this journey? We’d be very interested in knowing how you get on. We’re doing a lot of work at the moment, at Red Gate, trying to help people progress through these stages. For example, if you’re currently not source controlling your database, then this is a natural next step. If you are already source controlling your database, what about the next stage – continuous integration and automated release management? To help understand these issues, there’s a summary of the Red Gate Database Delivery learning program on our site, alongside a Patterns and Practices library here on Simple-Talk and a Training Academy section on our documentation site to help you get up and running with the tools you need to progress. All feedback is welcome and it would be great to hear where you find yourself on this journey! This article is part of our database delivery patterns & practices series on Simple Talk. Find more articles for version control, automated testing, continuous integration & deployment.

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• What does your Lisp workflow look like?

  - by Duncan Bayne

  I'm learning Lisp at the moment, coming from a language progression that is Locomotive BASIC - Z80 Assembler - Pascal - C - Perl - C# - Ruby. My approach is to simultaneously: write a simple web-scraper using SBCL, QuickLisp, closure-html, and drakma watch the SICP lectures I think this is working well; I'm developing good 'Lisp goggles', in that I can now read Lisp reasonably easily. I'm also getting a feel for how the Lisp ecosystem works, e.g. Quicklisp for dependencies. What I'm really missing, though, is a sense of how a seasoned Lisper actually works. When I'm coding for .NET, I have Visual Studio set up with ReSharper and VisualSVN. I write tests, I implement, I refactor, I commit. Then when I'm done enough of that to complete a story, I write some AUATs. Then I kick off a Release build on TeamCity to push the new functionality out to the customer for testing & hopefully approval. If it's an app that needs an installer, I use either WiX or InnoSetup, obviously building the installer through the CI system. So, my question is: as an experienced Lisper, what does your workflow look like? Do you work mostly in the REPL, or in the editor? How do you do unit tests? Continuous integration? Packaging & deployment? When you sit down at your desk, steaming mug of coffee to one side and a framed photo of John McCarthy to the other, what is it that you do? Currently, I feel like I am getting to grips with Lisp coding, but not Lisp development ...

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• Radeon HD 6850 VMware 3D Support?

  - by Matt

  I'm a new Ubuntu user (new to all of linux actually). I've installed Ubuntu 11.10 x64 and have been enjoying it, but I wanted to see how it would perform using VMware for small time gaming since I find dual booting too much of a nuisance to even bother using Ubuntu at all (sorry!). I have an Asus EAH6850 DirectCU Radeon HD 6850 graphics card and I've installed the additional ATI/AMD proprietary FGLRX graphics driver, but when I open a Windows XP 32bit machine I installed through VMware, I get this message: "The GPU driver currently installed on this host may cause issues with VMware products. If you notice any issues please disable the 3D support in the affected virtual machines." I still have 3D capabilities in the VM but they are very very choppy even running the DX tests (the spinning cube). I've seen people on youtube and other forums saying that since the new 3D acceleration in VMware 8 gaming is very possible through VMs (and I've seen them running the DX tests with the spinning cube very smoothly). I'm wondering if my graphics card isn't fully supported or if I have installed it wrong. Also when I check system info (on the host Ubuntu machine) it says "Graphics VESA:BARTS" Should my Radeon HD 6850 be showing up there? The rest of my basic system info i5 2500k 8GB 1600MHz memory Guest is running with access to all 4 cores of processor and 3gb memory assigned.

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• What's the best structure for a repository?

  - by jpmelos

  I've looked into many open source software repositories, and I've found some common elements and somethings people do in different fashion from one another. For example, every repository has a README file, a INSTALL file, a COPYING file and stuff like that. Other things differ: Some projects, like git, have their source code in the root level, while others have the source code in a src/ folder and others, like the Linux kernel, have the source code spread in different folders in root level, that divide code by areas; Some have their tests in a t/ folder, while others in a tests/ folder, or named otherwise; Some have files about submitting patches and who the maintainers are, and those might be inside some Documentation/ or in the root level. Are there recommendations? A best practice? For example: personally, I don't like the code in the root level, git-fashion. It looks messy and confuses one trying to start as a contributor (especially because they have some code inside folders, and scripts in the root level as well, it's really messy). If I were to start a project of my own and wanted to start right from the start, are there recommendations? Best practices? How can I make a clean and clear structure? Thank you!

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• Collision Detection for a 2D RPG

  - by PHMitrious

  First of all, I have done some research on this topic before asking, and I'm asking this question as a mean to get some opinions on this topic, so I don't make a decision only on my own, but taking into account other people's experience as well. I'm starting a 2D online RPG project. I am using SFML for graphics and input and I'm creating a basic game structure and all for the game, creating modules for each part of the game. Well, let me get to the point I just wanted to give you guys some context. I want to decide on how I'm going to work with collision detection. Well I'm kinda going to work on maps with a tile map divided in layers (as usual) and add an extra 2 layers - not exactly in the map - for objects. So I'll have collisions between objects and agents (players - npcs - monsters - spells etc) and agents and tiles. The seconds one can be easily solved the first one need a little bit of work. I considered both creating a basic collision test engine using polygons and a quadtree to diminish tests since I'm going to be working with big maps with lots of objects - creating both a physical and graphical world representation. And I also considered using a physics engine like Box2D for collision tests. I think the first approach would take more work on my part but the second one would have the overhead of using a whole physics engine for just collision detection and no physics. What do you guys think ?

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• Missing Package: header, Problem with MergeList, The package lists or status file could not be parsed or opened

  - by Inbar Rose

  THIS IS NOT A DUPLICATE OF SIMILAR QUESTIONS (like this) I just had to write that first, there are tons of questions similar to this, all of them have the same redirect to an answer that does not solve my problem, because I don't have the same problem, just the same symptom. I write tests for my companies application. One of these tests tries to upgrade the application from a previous version to a new version to make sure nothing breaks. When I am installing an old version of the application, some weird stuff starts to happen. Sometimes everything goes Okay, and nothing is wrong, other times when trying to install I get this message (company app name censored): E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/XXX-amd64_Packages E: The package lists or status file could not be parsed or opened. Using the solutions provided in the questions similar to this one (like this). Do not help, and the problem keeps repeating itself once it happens the first time. This has led me to believe something is wrong on the apt server where the package is being created, but searching these errors yields no information on anything beyond the "fix" suggested in the question I linked, the only other source of information I could find also did not help (here): So I am asking for information; What is the actual problem? What causes the problem? What can fix the problem? I hope this question is in good format, if there is a problem, or missing information I can move to chat.

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• Unity throws SynchronizationLockException while debugging

  - by pjohnson

  I've found Unity to be a great resource for writing unit-testable code, and tests targeting it. Sadly, not all those unit tests work perfectly the first time (TDD notwithstanding), and sometimes it's not even immediately apparent why they're failing. So I use Visual Studio's debugger. I then see SynchronizationLockExceptions thrown by Unity calls, when I never did while running the code without debugging. I hit F5 to continue past these distractions, the line that had the exception appears to have completed normally, and I continue on to what I was trying to debug in the first place.In settings where Unity isn't used extensively, this is just one amongst a handful of annoyances in a tool (Visual Studio) that overall makes my work life much, much easier and more enjoyable. But in larger projects, it can be maddening. Finally it bugged me enough where it was worth researching it.Amongst the first and most helpful Google results was, of course, at Stack Overflow. The first couple answers were extensive but seemed a bit more involved than I could pull off at this stage in the product's lifecycle. A bit more digging showed that the Microsoft team knows about this bug but hasn't prioritized it into any released build yet. SO users jaster and alex-g proposed workarounds that relieved my pain--just go to Debug|Exceptions..., find the SynchronizationLockException, and uncheck it. As others warned, this will skip over SynchronizationLockExceptions in your code that you want to catch, but that wasn't a concern for me in this case. Thanks, guys; I've used that dialog before, but it's been so long I'd forgotten about it.Now if I could just do the same for Microsoft.CSharp.RuntimeBinder.RuntimeBinderException... Until then, F5 it is.

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• NEW! Oracle Unified Business Process Management Specialization!

  - by michaela.seika(at)oracle.com

  Be one of the very first to become an Oracle Unified Business Process Management Specialist! Check out the Oracle Unified Business Process Management Knowledge Zone and go to the Specialization criteria to learn how you can become an BPM Specialized Partner. Pass the following assessment tests and exam to meet the competency criteria: · Oracle Unified Business Process Management Suite 11g Sales Specialist · Oracle Unified Business Process Management Suite 11g PreSales Specialist Assessment · Oracle Unified Business Process Management Suite 11g Essentials (1Z1-560) Exam Go to the OPN Competency Center to access the Specialist Guided Leaning Paths and Boot Camp to get the product information that can help you pass the tests: · Oracle Unified Business Process Management 11g Sales Specialist GLP · Oracle Unified Business Process Management 11g PreSales Specialist GLP · Oracle Unified Business Process Management 11g Implementation Specialist GLP · Oracle Unified Business Process Management Suite 11g Implementation Boot Camp Oracle Unified Business Process Management Suite 11g Essentials (1Z1-560) Exam is available in beta testing. Pass the exam to become an Oracle Unified Business Process Management Certified Implementation Specialist! As an incentive we are offering FREE beta exam vouchers to early-adopter Partners. As there are a limited number of free vouchers available, the requests will be processed on a first-come, first-served basis. To request a voucher send an e-mail to: [email protected] specifying the exam name, and your contact information: name, job role, and company name. Register for the OU beta exam at the nearest Pearson VUE testing center. For More Information Oracle Certification Program Beta Exams OPN Certified Specialist exams OPN Certified Specialist FAQ

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• HTML5 media loading sometimes suspends or aborts: misconfigured Apache?

  - by Joan Botella

  Recently, some code that has been working fine for months started to run unexpectedly. That code is just a media files loading JavaScript function, that uses jQuery. It's pretty long, but in essence it is like this: var $audio=$('<audio>'); $audio.on('canplaythrough',function(e){ $audio[0].play(); }); $audio.attr('src','song.ogg'); Basically, the file only loads sometimes, and sometimes stops loading with a suspend or even an abort event. I have uploaded a little testing HTML to http://www.joanbotella.com/tests/loading , where you can see what's happening. You can download the test files from http://www.joanbotella.com/tests/loading/loadingTest.zip for local testing. I have just checked that opening the test index.html file directly into Firefox, and not through my localhost Apache server, makes the audio files perfectly playable. So, I assume, my hosting and I have the Apache server misconfigured for serving media files. My software versions are: Apache 2.2.22-1ubuntu1.7 , Mozilla Firefox 31.0 , Chromium 36.0.1985.125 and jQuery 1.11.0. Can you help me? Thanks in advance!

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• How do I separate codes with classes?

  - by Trycon

  I have this main class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.SlickException; import org.newdawn.slick.state.BasicGameState; import org.newdawn.slick.state.StateBasedGame; public class tests extends BasicGameState{ public boolean render=false; tests1 test = new tests1(); public tests(int test) { // TODO Auto-generated constructor stub } @Override public void init(GameContainer arg0, StateBasedGame arg1) throws SlickException { // TODO Auto-generated method stub } @Override public void render(GameContainer arg0, StateBasedGame arg1, Graphics g) throws SlickException { // TODO Auto-generated method stub if(render==true) { g.drawString("Hello",100,100); } } @Override public void update(GameContainer gc, StateBasedGame s, int delta) throws SlickException { // TODO Auto-generated method stub test.render=render; test.update(gc, s, delta); } @Override public int getID() { // TODO Auto-generated method stub return 1000; } } and its sub-class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Input; import org.newdawn.slick.state.StateBasedGame; public class tests1 { public boolean render; public void update(GameContainer gc, StateBasedGame s, int delta) { Input input = gc.getInput(); if(input.isKeyPressed(Input.KEY_X)) { render=true; } } } I was finding a way to prevent many codes in one class. I'm new to java. When I try running my game, then when I press X, it does not work. How am I suppose to fix that?

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• How to add a new developer to the team

  - by lortabac

  I run a small company composed of only 2 developers. For one of our clients we are building a very big application, whose development has gone on for 1.5 years. Now this client has found an important sponsorship, and they are organizing some events related to this project, so we have a deadline in 2 months and we can't miss it. We are thinking of adding a new developer to the team, and I am wondering what we can do to help his integration. This is the situation: We are approaching the threshhold of Brooks's law, the point when adding new developers will be counter-productive. The application is relatively well designed, but the implementation is chaotic in some points (especially older code). There are unit tests only for more recent code. When this project started, we didn't have the habit of doing tests. Documentation and comments are incomplete. The application is both large and complex. The client has written down almost every detail about his project, in a very clear and "programmer-friendly" way. Is it a good idea to add a person now? If so, what can we do in order to help the new developer integrate into the team?

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