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• Could I be going crazy with Event Handlers? Am I going the "wrong way" with my design?

  - by sensae

  I guess I've decided that I really like event handlers. I may be suffering a bit from analysis paralysis, but I'm concerned about making my design unwieldy or running into some other unforeseen consequence to my design decisions. My game engine currently does basic sprite-based rendering with a panning overhead camera. My design looks a bit like this: SceneHandler Contains a list of classes that implement the SceneListener interface (currently only Sprites). Calls render() once per tick, and sends onCameraUpdate(); messages to SceneListeners. InputHandler Polls the input once per tick, and sends a simple "onKeyPressed" message to InputListeners. I have a Camera InputListener which holds a SceneHandler instance and triggers updateCamera(); events based on what the input is. AgentHandler Calls default actions on any Agents (AI) once per tick, and will check a stack for any new events that are registered, dispatching them to specific Agents as needed. So I have basic sprite objects that can move around a scene and use rudimentary steering behaviors to travel. I've gotten onto collision detection, and this is where I'm not sure the direction my design is going is good. Is it a good practice to have many, small event handlers? I imagine going the way I am that I'd have to implement some kind of CollisionHandler. Would I be better off with a more consolidated EntityHandler which handles AI, collision updates, and other entity interactions in one class? Or will I be fine just implementing many different event handling subsystems which pass messages to each other based on what kind of event it is? Should I write an EntityHandler which is simply responsible for coordinating all these sub event handlers? I realize in some cases, such as my InputHandler and SceneHandler, those are very specific types of events. A large portion of my game code won't care about input, and a large portion won't care about updates that happen purely in the rendering of the scene. Thus I feel my isolation of those systems is justified. However, I'm asking this question specifically approaching game logic type events.

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• Configuring trace file size and number in WebCenter Content 11g

  - by Kyle Hatlestad

  Lately I've been doing a lot of debugging using the System Output tracing in WebCenter Content 11g.  This is built-in tracing in the content server which provides a great level of detail on what's happening under the hood.  You can access the settings as well as a view of the tracing by going to Administration -> System Audit Information.  From here, you can select the tracing sections to include.  Some of my personal favorites are searchquery,  systemdatabase, userstorage, and indexer.  Usually I'm trying to find out some information regarding a search, database query, or user information.  Besides debugging, it's also very helpful for performance tuning. One of the nice tricks with the tracing is it honors the wildcard (*) character.  So you can put in 'schema*' and gather all of the schema related tracing.  And you can notice if you select 'all' and update, it changes to just a *.   To view the tracing in real-time, you simply go to the 'View Server Output' page and the latest tracing information will be at the bottom. This works well if you're looking at something pretty discrete and the system isn't getting much activity.  But if you've got a lot of tracing going on, it would be better to go after the trace log file itself.  By default, the log files can be found in the <content server instance directory>/data/trace directory. You'll see it named 'idccs_<managed server name>_current.log.  You may also find previous trace logs that have rolled over.  In this case they will identified by a date/time stamp in the name.  By default, the server will rotate the logs after they reach 1MB in size.  And it will keep the most recent 10 logs before they roll off and get deleted.  If your server is in a cluster, then the trace file should be configured to be local to the node per the recommended configuration settings. If you're doing some extensive tracing and need to capture all of the information, there are a couple of configuration flags you can set to control the logs. #Change log size to 10MB and number of logs to 20FileSizeLimit=10485760FileCountLimit=20 This is set by going to Admin Server -> General Configuration and entering them in the Additional Configuration Variables: section.  Restart the server and it should take on the new logging settings. 

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• 2012 EC Election Ballot open; Meet the Candidates Call tomorrow

  - by heathervc

  The JCP Executive Committee (EC) Election ballot is now open and all of the candidates' nominations materials are now available on JCP.org -- note that two new candidates were nominated late last week:  Liferay and North Sixty-One. It is shaping up to be an exciting election this year! The ratified candidates are:  Cinterion, Credit Suisse, Fujitsu and HP.The elected candidates are (9 candidates, 2 open seats):  Cisco Systems, CloudBees, Giuseppe Dell'Abate, Liferay, London Java Community, MoroccoJUG, North Sixty-One, Software AG, and Zero Turnaround. Tomorrow, 18 October, we will hold an open teleconference for the Java Community to meet the candidates and ask questions regarding their nomination.  We hope you will be able to participate in the call.  Should the time be inconvenient, a recording will be made available for download, and candidate questions may be posted on this blog entry or sent to [email protected]. Topic: Meet the EC Candidates Date: Thursday, October 18, 2012 Time: 9:30 am, Pacific Daylight Time (San Francisco, GMT-07:00) Meeting Number: 807 818 225 Meeting Password: MeetEC ------------------------------------------------------- To join the online meeting (Now from mobile devices) ------------------------------------------------------- 1. Go to https://jcp.webex.com/jcp/j.php?ED=186721592&UID=0&PW=NMmUzNjY5ZTMw&RT=MiM0 2. If requested, enter your name and email address. 3. If a password is required, enter the meeting password: MeetEC 4. Click "Join". To view in other time zones or languages, please click the link: https://jcp.webex.com/jcp/j.php?ED=186721592&UID=0&PW=NMmUzNjY5ZTMw&ORT=MiM0 ------------------------------------------------------- To join the audio conference only -------------------------------------------------------     +1 (866) 682-4770     Outside the US: global access numbers  https://www.intercallonline.com/portlets/scheduling/viewNumbers/listNumbersByCode.do?confCode=6279803 or +1 (408) 774-4073     Conference code: 9454597     Security code: JCPEC (52732)------------------------------------------------------- For assistance ------------------------------------------------------- 1. Go to https://jcp.webex.com/jcp/mc 2. On the left navigation bar, click "Support".

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• Hierachies....from the Top Down

  - by Joe G

  I've been struggling with how to write on the topic of the importance of hierarchy design.  It's not so much that hierarchies haven't always been important, it's more of that with Fusion, the timing of when the hierarchies are designed should take a higher priority.    I will attempt to explain..... When I was implementing applications, back in the day, we had the list of detailed account values to enter with the obvious parent accounts. Then, after the setup was complete and things were functioning, the reporting phase started.  Users explained the elements that they want on the reports, what totals should be included, and how things should be compared.  Frequently, there was at least one calculation that became a nightmare either because it was based on very specific things that didn't relate to anything else or because it was "hardcoded" so that when something changed, someone need to "fix" the report. With Fusion, the process changes slightly.  You still want to enter all of the detailed accounts, but before you start adding parent values, you should investigate the reporting requirements from the top-down.  It's better to build hierarchies based on the reporting requirements than it is to build reports based on random hierarchies. Build reports based on hierarchies that resemble the reports themselves, and maintain the hierarchies without rework of the reports. For example, if you look at an income statement, you may have line items for Material Costs, Employee Costs, Travel & Entertainment, and Total Operating Expenses.  In your hierarchy, you have detail values that roll up to Material Costs, Employee Costs, and Travel & Entertainment which roll up to Total Operating Expenses. Balances are stored automatically in the cube for each of these.  When you define the report, you pick each of these members - no calculations required.  If a new detail value is added, you simply add it to the hierarchy, and there is no need to modify the report. I realize that there are always exceptions that require special handling, but I am confident that you will end up with much fewer exceptions if you make reporting a priority and design your hierarchies from the top-down.

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• High-Powered Sites for low Cost

  - by HighAltitudeCoder

  Ahh, I am experiencing the intimidation of my very first post - visible by the whole world. Ok, here goes.   This first post is nothing exceptional.  It is simply a recommendation based (fittingly, I suppose) upon the job search you may be gearing up for.  I find myself in this very situation right now.  And, I will take my own recommendation after posting this entry. Job-Seekers: To the left you will notice two links under "Recommended Learning".  I have found these links to be invaluable when it comes to re-tooling, re-familiarizing, or otherwise resharping my skills when looking for that next job. Often, you will find job-postings with the text, usually posted after a laborious list of qualifications indicating the company's desire to hire candidates who know what they are doing: "...Looking for a candidate who can hit the ground running...".  The interesting thing about this post to me is I've encountered many individuals who, after speaking and working with them for some time, I've realized are perfectly capable of hitting the ground running - and FAST.  But what if they speed off in the wrong direction? The next time you spearhead a major task in your job, ask yourself: Am I headed in the wrong direction?  There are many ways to do this.  In fact, I've found in this new field there are more tempting ways to steer your project in the wrong direction than there are good ones.  I don't want to suggest that every one of my posts will fall into the "right direction" category, however I do think a healthy dose of introspection of the pros and cons will always be beneficial before you set off. That said, allow me to expound on the previously mentioned links. These web sites are invaluable.  They demonstrate the capabilities of existing as well as new and upcoming tools available in several IDE's.  I've viewed many tutorials in LearnVisualStudio.NET, and only one or two so far in TrainingSpot, however I've been delighted in their simplicity and straightforward approach to proper usage of the particular tool or concept being discussed.  They have not (so far in my experience) demonstrated ways in which to use the tools that become cumbersome, impractical, or error-prone. Each website has step-by-step videos that can be paused, replayed, and most importantly, they are done in real time.  As the author is typing, the viewer gets to experience the coding experience from a first-person perspective, including syntax errors, unexpected behaviors, IDE setup idiosyncracies, everything.  A subtle value I've gained from these videos is that a certain degree of confusion and introspection is normal when working with new tools and exploring new paths.  They (as well as your own experience) are not to be feared, but enjoyed.  I highly recommend them. Good work, guys!

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• How do I create weapon attachments?

  - by Tron86

  My question is; I am developing a game for XNA and I am trying to create a weapon attachment for my player model. My player model loads the .md3 format and reads tags for attachment points. I am able to get the tag of my model's hand. And I am also able to get the tag of my weapon's handle. Each tag I am able to get the rotation and position of and this is how I am calculating it: Model.worldMatrix = Matrix.CreateScale(Model.scale) * Matrix.CreateRotationX(-MathHelper.PiOver2) * Matrix.CreateRotationY(MathHelper.PiOver2); Pretty simple, the player model has a scale and its orientation(it loads on its side so I just use a 90 degree X axis rotation, and a Y axis rotation to face away from the camera). I then calculate the torso tag on the lower body, which gives me a local coordinate at the waist. Then I take that matrix and calculate the tag_weapon in the upper body. This gives me the hand position in local space. I also get the rotation matrix from that tag that I store for later use. All this seems to work fine. Now I move onto my weapon: Matrix weaponWorld = Matrix.CreateScale(CurrentWeapon.scale) * Matrix.CreateRotationX(-MathHelper.PiOver2) * TagRotationMatrix * Matrix.CreateTranslation(HandTag.Position) * Matrix.CreateRotationY(PlayerRotation) * Matrix.CreateTranslation(CollisionBody.Position) * You may notice the weapon matrix gets rotated by 90 degress on the X axis as well. This is because they load in on their sides. Once again this seems pretty simple and follows the SRT order I keep reading about. My TagRotation matrix is the hand's rotation. HandTag.Position is its position in local space. CreateRotationY(PlayerRotation) is the player's rotation in world space, and the CollisionBody.Position is the player's world location. Everything seems to be in order, and almost works in game. However when the gun spawns and follows the player's hand it seems to be flipped on an axis every couple frames. Almost like the X or Y axis is being inversed then put right back. Its hard to explain and I am totally stumped. Even removing all my X axis fixes does nothing to solve the problem. Hopefully I explained everything enough as I am a bit new to this! Thanks!

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• Simulate 'Shock absorbtion' with tire rubber in PhysX (2.8.x)

  - by Mungoid

  This is a kinda tricky question and I fear there is no easy enough solution, but I figured I'd hit SE up before giving up on it and just doing what I can. A machine I am working on has no suspension or shocks or springs of any sort in the real machine, so you would think that when it drives over bumps, it would shake like crazy but because its tires (6 of them) are quite large they seem to absorb a lot of shock from the bumps. Part of this is because the machine is around 30k lbs and it just smashes/compresses any bumps in the ground down (This is another issue im still working on) and the other part is that the tires seem to have a lot of flex to them with a lot of air as well. So my current task is to simulate shock absorption in physx without visibly separating the tires from the spindle/axle.. I have been messing with all kinds of NxMaterial, NxSpring, Joints, etc. and have had no luck getting this to work. The main problem is that the spindle attached to the tire is directly in the center and the axle is basically solidly attached to the chassis, so if i give it any spring or suspension travel, that spindle on the tires will move upwards or downwards, looking very odd because now its not any longer in the center of the tire. I tried giving it a higher restitution but that just makes it bouncy without any shock absorption. Another avenue I am messing with is to actively smooth the terrain in front of the tires so that before it hits a bumpy patch, that patch is smoothed and it doesn't bounce. The only issue with this is that it is pretty expensive to do with 6 tires, high tesselation of the terrain and other complex things going on at the same time in this simulation. I am still working on this but I am hoping to mix and match a few different aspects to get the best possible outcome. This is a bit of a complex issue so I'm not expecting anyone to have a definitive answer, just hoping someone may think of something I haven't =-) -Side note: Yes i know PhysX 2.8.x is quite outdated but we have to stick with it for this implementation. We are in the process of going to another physics engine but it is out of scope to apply that engine to this project.

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• Practices for domain models in Javascript (with frameworks)

  - by AndyBursh

  This is a question I've to-and-fro'd with for a while, and searched for and found nothing on: what're the accepted practices surrounding duplicating domain models in Javascript for a web application, when using a framework like Backbone or Knockout? Given a web application of a non-trivial size with a set of domain models on the server side, should we duplicate these models in the web application (see the example at the bottom)? Or should we use the dynamic nature to load these models from the server? To my mind, the arguments for duplicating the models are in easing validation of fields, ensuring that fields that expected to be present are in fact present etc. My approach is to treat the client-side code like an almost separate application, doing trivial things itself and only relying on the server for data and complex operations (which require data the client-side doesn't have). I think treating the client-side code like this is akin to separation between entities from an ORM and the models used with the view in the UI layer: they may have the same fields and relate to the same domain concept, but they're distinct things. On the other hand, it seems to me that duplicating these models on the server side is a clear violation of DRY and likely to lead to differing results on the client- and server-side (where one piece gets updated but the other doesn't). To avoid this violation of DRY we can simply use Javascripts dynamism to get the field names and data from the server as and when they're neeed. So: are there any accepted guidelines around when (and when not) to repeat yourself in these situations? Or this a purely subjective thing, based on the project and developer(s)? Example Server-side model class M { int A DateTime B int C int D = (A*C) double SomeComplexCalculation = ServiceLayer.Call(); } Client-side model function M(){ this.A = ko.observable(); this.B = ko.observable(); this.C = ko.observable(); this.D = function() { return A() * C(); } this.SomeComplexCalculation = ko.observalbe(); return this; }l M.GetComplexValue = function(){ this.SomeComplexCalculation(Ajax.CallBackToServer()); }; I realise this question is quite similar to this one, but I think this is more about almost wholly untying the web application from the server, where that question is about doing this only in the case of complex calculation.

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• How to write comments to explain the "why" behind the callback function when the function and parameter names are insufficient for that?

  - by snowmantw

  How should I approach writing comments for callback functions? I want to explain the "why" behind the function when the function and parameter names are insufficient to explain what's going on. I have always wonder why comments like this can be so ordinary in documents of libraries in dynamic languages: /** * cb: callback // where's the arguments & effects? */ func foo( cb ) Maybe the common attitude is "you can look into source code on your own after all" which pushes people into leaving minimalist comments like this. But it seems like there should be a better way to comment callback functions. I've tried to comment callbacks in Haskell way: /** * cb: Int -> Char */ func foo(cb) And to be fair, it's usually neat enough. But it gets into trouble when I need to pass some complex structure. The problem being partly due to the lack of type system: /** * cb: Int -> { err: String -> (), success: () -> Char } // too long... */ func foo(cb) Or I have tried this too: /** * cb: Int -> { err: String -> (), * success: () -> Char } // better ? */ func bar(cb) The problem is that you may put the structure in somewhere else, but you must give it a name to reference it. But then when you name a structure you're about to use immediately looks so redundant: // Somewhere else... // ResultCallback: { err: String -> (), success: () -> Char } /** * cb: Int -> ResultCallback // better ?? */ func foo(cb) And it bothers me if I follow the Java-doc like commenting style since it still seems incomplete. The comments don't tell you anything that you couldn't immediately see from looking at the function. /** * @param cb {Function} yeah, it's a function, but you told me nothing about it... * @param err {Function} where should I put this callback's argument ?? * Not to mention the err's own arguments... */ func foo(cb) These examples are JavaScript like with generic functions and parameter names, but I've encountered similar problems in other dynamic languages which allow complex callbacks.

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• Testing and Validation – You Really Do Have The Time

  - by BuckWoody

  One of the great advantages in my role as a Technical Specialist here at Microsoft is that I get to work with so many great clients. I get to see their environments and how they use them, and the way they work with SQL Server. I’ve been a data professional myself for many years. Over that time I’ve worked with many database platforms, lots of client applications, and written a lot of code in many industries. For a while I was also a consultant, so I got to see how other shops did things as well. But because I now focus on a “set” base of clients (over 500 professionals in over 150 companies) I get to see them over a longer period of time. Many of them help me understand how they use the product in their projects, and I even attend some DBA regular meetings. I see the way the product succeeds, and I see when it fails. Something that has really impacted my way of thinking is the level of importance any given shop is able to place on testing and validation. I’ve always been a big proponent of setting up a test system and following a very disciplined regimen to make sure it will work in production for any new projects, and then taking the lessons learned into production as standards. I know, I know – there’s never enough time to do things right like this. Yet the shops I see that do it have the same level of work that they output as the shops that don’t. They just make the time to do the testing and validation and create a standard that they will follow in production. And what I’ve found (surprise surprise) is that they have fewer production problems. OK, that might seem obvious – but I’ve actually tracked it and those places that do the testing and best practices really do save stress, time and trouble from that effort. We all think that’s a good idea, but we just “don’t have time”. OK – but from what I’m seeing, you can gain time if you spend a little up front. You may find that you’re actually already spending the same amount of time that you would spend in doing the testing, you’re just doing it later, at night, under the gun. Food for thought.  Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• How best to look up objects by label?

  - by dsollen

  I am writing the server backed by a pre-written API. I'm going to get a number of strings representing ports, signals, paths, etc etc etc. I need to look up the object associated with a given label, these objects are all in memory (no sql magic to do this for me). My question is, how best do I associate a given unique label with the mutable object it represents? I have enough objects that looking through every signal or every port to find the one that matches is possible, but may be slightly too slow. To be honest the direct 'look at every object' method is probably good enough for so small a body of objects and anything else is premature optimization, but I still am curious what the proper solution would be if I thought my signals were going to grow a bit larger. As I see it there are two options available. First would be to to create a 'store' that is a simple map between object and label. I could have it so that every time I call addObject the object is automatically saved into a hashmap or the like. This works, but relies on my properly adding and deleting each object so the map doesn't grow indefinitely. The biggest issue to me is that this involves having some hidden static map in my ModelObject class that just feels...wrong somehow. The other option is to have some method that can interpret the labels. All of these labels are derived from the underlying objects. So I can look at the signal label, for instance, and say "these 20 characters are the port" to figure out what port I need. This would allow me to quickly figure out what I need. However, if the label method is changed the translateLabelToObject method needs to be updated as well or everything breaks. Which solution is cleaner, or possibly a cleaner solution than either of above? For the record I'm working with sufficient number of variables to make direct comparison a little slow, but not enough to be concerned about memory overhead, written in java. All objects that have labels I need to look up extend the same parent class.

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• reference list for non-IT driven algorithmic patterns

  - by Quicker

  I am looking for a reference list for non-IT driven algorithmic patterns (which still can be helped with IT implementations of IT). An Example List would be: name; short desc; reference Travelling Salesman; find the shortest possible route on a multiple target path; http://en.wikipedia.org/wiki/Travelling_salesman_problem Ressource Disposition (aka Regulation); Distribute a limited/exceeding input on a given number output receivers based on distribution rules; http://database-programmer.blogspot.de/2010/12/critical-analysis-of-algorithm-sproc.html If there is no such list, but you instantly think of something specific, please 'put it on the desk'. Maybe I can compile something out of the input I get here (actually I am very frustrated as I did not find any such list via research by myself). Details on Scoping: I found it very hard to formulate what I want in a way everything is out that I do not need (which may be the issue why I did not find anything at google). There is a database centric definition for what I am looking for in the section 'Processes' of the second example link. That somehow fits, but the database focus sort of drifts away from the pattern thinking, which I have in mind. So here are my own thoughts around what's in and what's out: I am NOT looking for a foundational algo ref list, which is implemented as basis for any programming language. Eg. the php reference describes substr and strlen. That implements algos, but is not what I am looking for. the problem the algo does address would even exist, if there were no computers (or other IT components) the main focus of the algo is NOT to help other algo's chances are high, that there are implementions of the solution or any workaround without any IT support out there in the world however the algo could be benefitialy implemented/fully supported by a software application = means: the problem of the algo has to be addressed anyway, but running an algo implementation with software automates the process (that is why I posted it on stackoverflow and not somewhere else) typically such algo implementations have more than one input field value and more than one output field value - which implies it could not be implemented as simple function (which is fixed to produce not more than one output value) in a normalized data model often times such algo implementation outputs span accross multiple rows (sometimes multiple tables), whereby the number of output rows depends on the input paraters and rows in the table(s) at start time - which implies that any algo implementation/procedure must interact with a database (read and/or write) I am mainly looking for patterns, not for specific implementations. Example: The Travelling Salesman assumes any coordinates, however it does not say: You need a table targets with fields x and y. - however sometimes descriptions are focussed on examples with specific implementations very much - no worries, as long as the pattern gets clear

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• Java Grade Calculator program for class kepp geting the error "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." [migrated]

  - by user2880621

  this is my first question I've posted. I've used this site to look at other questions to help with similar problems I've had. After some cursory looking I couldn't find quite the answer I was looking for so I decided to finally succumb and create an account. I am fairly new to java, only a few weeks into my first class. Anyway, my project is to create a program which takes any amount of students and their grades, and then assign them a letter grade. The catch is, however, that it is on a sort of curve and the other grades' letter are dependent on the the highest. Anything equal to or 10 points below the best grade is an a, anything 11-20 points below is a b, and so on. I am to use an array, but I get this error when ran "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." I will go ahead and post my code down below. Thanks for any advice you may be able to give. package grade.calculator; import java.util.Scanner; /** * * @author nichol57 */ public class GradeCalculator { /** * @param args the command line arguments */ public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println("Enter the number of students"); int number = input.nextInt(); double[]grades = new double [number]; for (int J = number; J >=0; J--) { System.out.println("Enter the students' grades"); grades[J] = input.nextDouble(); } double best = grades[0]; for (int J = 1; J < number; J++) { if (grades[J] >= best){ best = grades[J]; } } for (int J = 0;J < number; J++){ if (grades[J] >= best - 10){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "A"); } else if (grades[J] >= best - 20){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "B"); } else if (grades[J] >= best - 30) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "C"); } else if (grades[J] >= best - 40) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "D"); } else { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "F"); } } // end for loop for output }// end main method }

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• Raid superblock missing on single parition. Recovery needed!

  - by user171639

  Ok so I have a 2 TB raid 1 setup that has three partitions: sdc1: linux sdc2: swap sdc3: LVM for data However the LVM will no longer mount. So I thought that I would take the first drive, mount it in linux (ive done this b4), and reset the spare drive to copy the data. Normally I can mount a single drive for data recovery using: sudo su apt-get install mdadm lvm2 mdadm --assemble --scan modprobe dm-mod vgscan vgchange -ay c mount -o ro /dev/c/c /mnt Unfortunately, vgscan doesnot recognize the data partition. It appears as though the superblock on the first drive's data partition was erased while syncing with the second. So now I cannot mount that partition and the second drive is stuck in spare mode. Any ideas? Or a way to force mount the data partition just to copy the data? knoppix@Microknoppix:~$ sudo su root@Microknoppix:/home/knoppix# apt-get install mdadm lvm2 Reading package lists... Done Building dependency tree Reading state information... Done lvm2 is already the newest version. mdadm is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 551 not upgraded. root@Microknoppix:/home/knoppix# mdadm --assemble --scan mdadm: /dev/md/1 has been started with 1 drive (out of 2). mdadm: /dev/md/0 has been started with 1 drive (out of 2). root@Microknoppix:/home/knoppix# modprobe dm-mod root@Microknoppix:/home/knoppix# vgscan Reading all physical volumes. This may take a while... No volume groups found root@Microknoppix:/home/knoppix# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdc1[2] 4193268 blocks super 1.2 [2/1] [U_] md1 : active raid1 sdc2[2] 524276 blocks super 1.2 [2/1] [U_] unused devices: <none> root@Microknoppix:/home/knoppix# mdadm -v --assemble --auto=yes /dev/md2 /dev/sdc3 mdadm: looking for devices for /dev/md2 mdadm: no recogniseable superblock on /dev/sdc3 mdadm: /dev/sdc3 has no superblock - assembly aborted root@Microknoppix:/home/knoppix# dumpe2fs /dev/md0 | grep -i superblock dumpe2fs 1.42.4 (12-Jun-2012) Primary superblock at 0, Group descriptors at 1-1 Backup superblock at 32768, Group descriptors at 32769-32769 Backup superblock at 98304, Group descriptors at 98305-98305 Backup superblock at 163840, Group descriptors at 163841-163841 Backup superblock at 229376, Group descriptors at 229377-229377 Backup superblock at 294912, Group descriptors at 294913-294913 Backup superblock at 819200, Group descriptors at 819201-819201 Backup superblock at 884736, Group descriptors at 884737-884737 root@Microknoppix:/home/knoppix# Notes: I can read the super block from the spare drive. I was gonna try and restore the superblock from one of the backups, but i dont know how or if this would work. I also heard creating a new array (mdadm --create) using the same parameters will not delete the data on the drive but i didnt want to risk it. Recommendations?

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• Are there any good Java/JVM libraries for my Expression Tree architecture?

  - by Snuggy

  My team and I are developing an enterprise-level application and I have devised an architecture for it that's best described as an "Expression Tree". The basic idea is that the leaf nodes of the tree are very simple expressions (perhaps simple values or strings). Nodes closer to the trunk will get more and more complex, taking the simpler nodes as their inputs and returning more complex results for their parents. Looking at it the other way, the application performs some task, and for this it creates a root expression. The root expression divides its input into smaller units and creates child expressions, which when evaluated it can use to build it's own result. The subdividing process continues until the simplest leaf nodes. There are two very important aspects of this architecture: It must be possible to manipulate nodes of the tree after it is built. The nodes may be given new input values to work with and any change in result for that node needs to be propagated back up the tree to the root node. The application must make best use of available processors and ultimately be scalable to other computers in a grid or in the cloud. Nodes in the tree will often be updating concurrently and notifying other interested nodes in the tree when they get a new value. Unfortunately, I'm not at liberty to discuss my actual application, but to aid understanding a little bit, you might imagine a kind of spreadsheet application being implemented with a similar architecture, where changes to cells in the table are propagated all over the place to other cells that need the result. The spreadsheet could get so massive that applying multi-core multi-computer distributed system to solve it would be of benefit. I've got my prototype "Expression Engine" working nicely on a single multi-core PC but I've started to run into a few concurrency issues (as expected because I haven't been taking too much care so far) so it's now time to start thinking about migrating the Engine to a more robust library, and that leads to a number of related questions: Is there any precedent for my "Expression Tree" architecture that I could research? What programming concepts should I consider. I realise this approach has many similarities to a functional programming style, and I'm already aware of the concepts of using futures and actors. Are there any others? Are there any languages or libraries that I should study? This question is inspired by my accidental discovery of Scala and the Akka library (which has good support for Actors, Futures, Distributed workloads etc.) and I'm wondering if there is anything else I should be looking at as well?

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• Is it dangerous for me to give some of my Model classes Control-like methods?

  - by Pureferret

  In my personal project I have tried to stick to MVC, but I've also been made aware that sticking to MVC too tightly can be a bad thing as it makes writing awkward and forces the flow of the program in odd ways (i.e. some simple functions can be performed by something that normally wouldn't, and avoid MVC related overheads). So I'm beginning to feel justified in this compromise: I have some 'manager programs' that 'own' data and have some way to manipulate it, as such I think they'd count as both part of the model, and part of the control, and to me this feels more natural than keepingthem separate. For instance: One of my Managers is the PlayerCharacterManager that has these methods: void buySkill(PlayerCharacter playerCharacter, Skill skill); void changeName(); void changeRole(); void restatCharacter(); void addCharacterToGame(); void createNewCharacter(); PlayerCharacter getPlayerCharacter(); List<PlayerCharacter> getPlayersCharacter(Player player); List<PlayerCharacter> getAllCharacters(); I hope the mothod names are transparent enough that they don't all need explaining. I've called it a manager because it will help manage all of the PlayerCharacter 'model' objects the code creates, and create and keep a map of these. I may also get it to store other information in the future. I plan to have another two similar classes for this sort of control, but I will orchestrate when and how this happens, and what to do with the returned data via a pure controller class. This splitting up control between informed managers and the controller, as opposed to operating just through a controller seems like it will simplify my code and make it flow more. My question is, is this a dangerous choice, in terms of making the code harder to follow/test/fix? Is this somethign established as good or bad or neutral? I oculdn't find anything similar except the idea of Actors but that's not quite why I'm trying to do. Edit: Perhaps an example is needed; I'm using the Controller to update the view and access the data, so when I click the 'Add new character to a player button' it'll call methods in the controller that then go and tell the PlayerCharacterManager class to create a new character instance, it'll call the PlayerManager class to add that new character to the player-character map, and then it'll add this information to the database, and tell the view to update any GUIs effected. That is the sort of 'control sequence' I'm hoping to create with these manager classes.

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• How to do proper Alpha in XNA?

  - by Soshimo

  Okay, I've read several articles, tutorials, and questions regarding this. Most point to the same technique which doesn't solve my problem. I need the ability to create semi-transparent sprites (texture2D's really) and have them overlay another sprite. I can achieve that somewhat with the code samples I've found but I'm not satisfied with the results and I know there is a way to do this. In mobile programming (BREW) we did it old school and actually checked each pixel for transparency before rendering. In this case it seems to render the sprite below it blended with the alpha above it. This may be an artifact of how I'm rendering the texture but, as I said before, all examples point to this one technique. Before I go any further I'll go ahead and paste my example code. public void Draw(SpriteBatch batch, Camera camera, float alpha) { int tileMapWidth = Width; int tileMapHeight = Height; batch.Begin(SpriteSortMode.Texture, BlendState.AlphaBlend, SamplerState.PointWrap, DepthStencilState.Default, RasterizerState.CullNone, null, camera.TransformMatrix); for (int x = 0; x < tileMapWidth; x++) { for (int y = 0; y < tileMapHeight; y++) { int tileIndex = _map[y, x]; if (tileIndex != -1) { Texture2D texture = _tileTextures[tileIndex]; batch.Draw( texture, new Rectangle( (x * Engine.TileWidth), (y * Engine.TileHeight), Engine.TileWidth, Engine.TileHeight), new Color(new Vector4(1f, 1f, 1f, alpha ))); } } } batch.End(); } As you can see, in this code I'm using the overloaded SpriteBatch.Begin method which takes, among other things, a blend state. I'm almost positive that's my problem. I don't want to BLEND the sprites, I want them to be transparent when alpha is 0. In this example I can set alpha to 0 but it still renders both tiles, with the lower z ordered sprite showing through, discolored because of the blending. This is not a desired effect, I want the higher z-ordered sprite to fade out and not effect the color beneath it in such a manner. I might be way off here as I'm fairly new to XNA development so feel free to steer me in the correct direction in the event I'm going down the wrong rabbit hole. TIA

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• Employer admits that its developers are underpaid and undervalued. Time to part ways?

  - by Psionic

  My employer recently posted an opening for a C# Developer with 3-5 years of experience. The requirements and expectations for the position were fair, up until the criteria for salary determination. It was stated clearly that compensation would depend ONLY on experience with C#, and that years of programming experience with other languages & frameworks would be considered irrelevant and not factored in. I brought up my concern with HR that good candidates would see this as a red flag and steer away. I attempted to explain that software development is about much more than specific languages, and that paying someone for their experience in a single language is a very shortsighted approach to hiring good developers (I'm telling this to the HR dept of a software company). The response: "We are tired of wasting time interviewing developers who expect 'big salaries' because they have lots of additional programming experience in languages other than what we require." The #1 issue here is that 'big salaries' = Market Rate. After some serious discussion, they essentially admitted that nobody at the company is paid near market rate for their skills, and there's nothing that can be done about it. The C-suite has the mentality that employees should only be paid for skills proven over years under their watch. Entry-level developers are picked up for less than $38K and may reach 50K after 3 years, which I'm assuming is around what they plan on offering candidates for the C# position. Another interesting discovery (not as relevant) - people 'promoted' to higher responsibilities do not get raises. The 'promotion' is considered an adjustment of the individuals' roles to better suit their 'strengths', which is what they're already being paid for. After hearing these hard truths straight from HR, I would assume that most people who are looking out for themselves would quickly begin searching for a new employer that has a better idea of what they're doing in the industry (this company fails in many other ways, but I don't want to write a book). Here is my dilemma however: This is the first official software development position I've held, for barely 1 year now. My previous position of 3 years was with a very small company where I performed many duties, among them software development (not in my official job description, but I tried very hard to make it so). I've identified local openings that I'm currently qualified for, most paying at least 50% more than I'm getting now. Question is, is it too soon for a jump? I am getting valuable experience in my current position, with no shortage of exciting projects. The work environment is very comfortable, and I'm told by many that I'm in the spotlight of the C-level guys for the stuff that I've been able to accomplish during my short time (for what that's worth). However, there is a clear opportunity cost to staying, knowing now with certainty that I will have to wait 3-5 years only to be capped at what I could potentially be earning elsewhere this year. I am also aware that 'job hopper' is a dangerous label to have, regardless of the reasons.

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• Response: Agile's Second Chasm

  - by Malcolm Anderson

  William Pietri over at Agile Focus has written an interesting article entitled, "Agile’s Second Chasm (and how we fell in)" in which he talks about how agile development has fallen into a common trap where large companies are now spending a lot of money hiring agile (Scrum) consultants just so that they can say they are agile, but all the while avoiding any change that is required by Scrum.   It echoes the questions that I've been asking for a while, "Can a fortune 500 company actually do agile development?"  I'm starting to think that the answer is "usually not"   William ask 3 questions at the end of his article that I will answer here.   1) Have I seen agile development brought in and then preemptively customized (read: made into ScrummerFall)?   Yes, Scrum is hard and disruptive.  It's a spotlight on company dysfunction.  In a low trust environment like most fortune 500 companies Scrum will be subverted by anyone who has ever seen "transparency" translate into someone being laid off.   2) If I had to do it all over again, would I change anything?  No, this is a natural progression, but the agile principles are powerful enough, that the companies that don't adopt them will no longer be competitive and will start to fail.   3) Is this situation solvable?  I think it is.  I think that one of the issues is that you often see companies implementing Scrum, but avoiding the agile engineering practices.  I believe that you cannot do one without the other.  Scrum keeps the ship sailing in smooth deep waters.  The agile engineering practices keep the engine running smoothly and cleanly.  If you implement agile engineering practices without Scrum, you run the risk of ending up with a great running piece of software that is useful to no one.  On the other hand, implementing cargo-cult Scrum without the agile engineering practices and you end up (especially in a fortune 500 company) being steered in the right direction, but with your development practices coming to a dead halt because you have code that can not keep up with the changes in requirements.   If you are trying to do Scrum, make sure that you hire some agile engineering coaches, or else you may find your deveolpment engines grinding to a dead halt in the middle of the open ocean.

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• 2d, Top-down map with different levels

  - by Ktash

  So, I'm creating a 2d, top down, sprite based (tiled) game, and right now I'm working on maps (well, a map editor at the moment, but it will be creating my maps, so basically the same thing). The scenario So, I'm thinking about efficiency and creating a map in pieces. In each piece, I plan on having 'layers'. Basically, I plan on rendering it down to a 'below hero' level, and an 'above hero' level, with the hero rendered in between obviously. There will likely also be a 'on level with hero' layer, but I'm not quite there yet. Not even worrying about events or interaction yet. Just looking to get a hero on the screen. Now for movement, I obviously need to know what tiles can be moved and in what direction. My plan at the moment is each tile getting 8 bits (4 'can enter in direction' bits, 4 'can leave in direction'). This will allow me to limit movement and even allow one way directional movement. The dilemma This works great for a lot of scenarios. It will allow me to store a map in essentially 3 layers, a string, and gives me flexibility going forward. However, I can't create maps that themselves have layers. A good example is a bridge where the user can go under or over the bridge without invalid moves being allowed. I can't create a platform and allow movement underneath. These are things I would like to be able to include in my game. My idea In theory, I could allow multiple hero layers and then allow multiple sets of 'below' and 'above' layers (or sandwich layers). But this complicates my system, and makes movement between maps potentially tricky (If the hero is on the third layer at the edge of a map, but that corresponds to the second layer on the other map, how can I allow or disallow movement). My question Is there a better way to manage multiple maps with multiple levels like this where a users level may be 'connected' on different levels on different maps? Or even... Am I doing this the hard way? Is there a more standard way to handle top-down 2d tiled maps that I am just not aware of? Things to note or that might be helpful This will be done in Javascript (transferred around in JSON) State will need to be transferred quickly, so a map-id and x/y/direction should be enough to get me a boolean 'can move' value Maps will not be standard sized (though they will be in a certain number of tiles) Making an editor tool so that I can have others help, so something that I can create in a tool would be helpful 'Teleportation' locations will likely need to exist to get into building maps and to and from different map sets (which will not necessarily be connected), but have not been created yet (lumping in with events at the moment).

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• Imperative vs. component based programming [closed]

  - by AlexW

  I've been thinking about how programming and more specifically the teaching of programming is advocated amongst the community (online). Often I've heard that Ruby and RoR is an ideal platform for learning to program. I completely disagree... RoR and Ruby are based on the application of the component based paradigm, which means they are ideal for rapid application development. This is much like the MVC model in PHP and ASP.NET But, learning a proper imperative language like Java or C/C++ (or even Perl and PHP) is the only way for a new programmer to explore logic itself, and not get too bogged down in architectural concerns like the need for separation of concerns, and the preference for components. Maybe it's a personal preference thing. I rather think that the most interesting aspects to programming are the procedural bits of code I write that actually do stuff rather than the project planning, and modelling that comes about from fully object oriented engineering or simply using the MVC model. I know this may sound confused to some of you. I feel strongly though that the best way for programming to be taught is through imperative and procedural methods. Architectural (component) methods come later, if at all. After all, none of the amazing algorithms that exist were based on OOP practice! It's all procedural code when it comes to the 'magic'. OOP is useful in creating products and utilities. Algorithms are what makes things happen, and move data around, and so imperative (and/or procedural) code are what matters most. When I see programmers recommending Ruby on Rails to newbie developers, I think it's just so wrong. Just because you write less code with Ruby does not make it easier to do! It's the opposite... you have to know loads more to appreciate its succinct nature. New coders who really want to understand the nuts and bolts of coding need to go away and figure out writing methods/functions (i.e. imperative programming) and working in procedural style, in order to grasp the fundamentals, first, before looking into architectural ways of working. So, my question is: should Ruby ever be recommended as a first language? I think no (obviously)... what arguments are there for it?

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• Lazy Processing of Streams

  - by Giorgio

  I have the following problem scenario: I have a text file and I have to read it and split it into lines. Some lines might need to be dropped (according to criteria that are not fixed). The lines that are not dropped must be parsed into some predefined records. Records that are not valid must be dropped. Duplicate records may exist and, in such a case, they are consecutive. If duplicate / multiple records exist, only one item should be kept. The remaining records should be grouped according to the value contained in one field; all records belonging to the same group appear one after another (e.g. AAAABBBBCCDEEEFF and so on). The records of each group should be numbered (1, 2, 3, 4, ...). For each group the numbering starts from 1. The records must then be saved somewhere / consumed in the same order as they were produced. I have to implement this in Java or C++. My first idea was to define functions / methods like: One method to get all the lines from the file. One method to filter out the unwanted lines. One method to parse the filtered lines into valid records. One method to remove duplicate records. One method to group records and number them. The problem is that the data I am going to read can be too big and might not fit into main memory: so I cannot just construct all these lists and apply my functions one after the other. On the other hand, I think I do not need to fit all the data in main memory at once because once a record has been consumed all its underlying data (basically the lines of text between the previous record and the current record, and the record itself) can be disposed of. With the little knowledge I have of Haskell I have immediately thought about some kind of lazy evaluation, in which instead of applying functions to lists that have been completely computed, I have different streams of data that are built on top of each other and, at each moment, only the needed portion of each stream is materialized in main memory. But I have to implement this in Java or C++. So my question is which design pattern or other technique can allow me to implement this lazy processing of streams in one of these languages.

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• Rolling With the Punches

  - by D'Arcy Lussier

  So I’ve been tweeting the last little while “Rolling with the punches” and I’ve had some people ask me what that meant. Whether you’re running a conference (like I am this week), or a project, or a birthday party for a 2 year old, you need to be ready to handle those things that are unexpected. Risk mitigation can only go so far and its at those times that you need to become resourceful. So let me tell you what the last few days have been like. Today is the first day of Prairie Dev Con Winnipeg, a conference that I run. On Friday I was informed that my keynote speaker had lost his voice, one of my speakers had a family emergency and had to back out, and I got a warning from another that he was travelling over the weekend and if there was a storm or something he may not be able to get back by Monday for his talk. A storm didn’t happen, but their car did break down and he was delayed. Finally, Saturday night I took my printing order to Staples. It was at 5 and they closed at 6, and I had a bunch of surveys to be printed and cut. The girl working said that she’d have it ready by the next day (Sunday). Her intent was to come in the next morning and finish the job. Unfortunately, she had to be hospitalized that night and never made it into work…and never informed anyone of the remaining work. They found out at 3pm when I came to pick it up and there was no way they’d be able to cut everything in time. So how did we roll with these punches? - Miguel, my keynote speaker, was a trooper and was able to do the keynote but asked that his session get moved from Monday to Tuesday. This is why I wait until the last day before printing out schedules, they can change up to the event and even later. - I was able to move some sessions around to accommodate my stranded speaker and fill the empty slot from the speaker that couldn’t make it. - Staples was able to get me half the cut surveys so I took those and my wife will pick up the rest today. I altered how we’d collect session surveys, and actually I think it’ll work better. So all of this is to say, plan but also plan for what you can’t plan for – there will be things that happen that blindside you, that you’re not sure how to handle or solve. Stop, take a deep breath, and don’t feel that you need to limit yourself to the boundaries that you initially set for yourself. Roll with the punch and learn from it so that you can avoid the blow next time. Now, back to the conference! D

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• ETPM Forms Accelerator

  - by MHundal

  The ETPM Forms Accelerator provides a template that can be used to enter data related to Registration and Tax Forms.  The Forms Accelerator includes a worksheet for each portion related to forms development (Form Type, Form Section, Form Lines and Form Rules).  The Forms Accelerator provides the details that must be defined in ETPM.  This allows for taking an existing form and translating the details of that form into the spreadsheet.  The spreadsheet can then be used to define the details in the system.  In addition, each of the items to be defined is explained it detail - what the field expects and based on the input, how it impacts the field and form definition.   This is a living document - as there is feedback provided, the document will be updated.  The goal of this accelerator is to be an aide in the Forms Development process.  We encourage feedback to help improve the document.  The document is for ETPM 2.3.1.  Implementations using older version of ETPM will find that some of the field definition options may not exist their current system.   The spreadsheet attached contains the following Worksheets: Instructions:  High-level overview for the different worksheets provided. Form Type:  The fields to be populated when defining the Form Type for a Registration or Tax Form Form Section:  The fields to be populated when creating a Form Section.  The number of sections will differ based on the the form being implemented. Form Lines:  The fields to be populated when creating different Form Lines. The number of lines per section will differ based on the form being implemented. Form Rules:  Based on the form, allows for documenting the Form Rules to be configured based on form instructions and Form Lines. Right click on the link and select the "Save Link As" option.  ETPM Forms Accelerator.xls Please provide feedback to [email protected]. You feedback is encouraged and appreciated.  

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• How can I improve the battery life under 12.04 on my Inspiron 14z? [duplicate]

  - by cfogelberg

  This question already has an answer here: Tips to extend battery life for laptops and notebooks 24 answers How do I improve the battery life of my Inspiron 14z under Ubuntu 12.04? This laptop gets 4-5 hours of battery life using Windows (e.g. here). I've removed Windows, installed Ubuntu 12.04 and the initial battery life was only 2 hours. With some tweaks (described below) it's still only ~2.5 hours. For reference, the laptop is the latest model of the 14z: i5-3337U processor 32GB MSATA, 500GB HDD (5400rpm) AMD Radeon HD7570M graphics card I have put ext4 partitions on both the SSD and the HDD, and have mounted / to the SSD and /home to the HDD. I also put a 24gb linux swap partition at the start of the HDD, though I figure this won't be used all that much (the laptop has 8gb of RAM). After googling around and reading Ask Ubuntu and other sites extensively, I have done the following steps, and they have improved the battery life ~30 minutes (exact improvement not clear, but battery life is still nowhere near 4-5 hours). Installed Jupiter (and set Performance to "Power Saving") Installed laptop-mode-tools cat /proc/sys/vm/laptop_mode now outputs 5 (previously it output 0) But it's not clear that this will help: AskUbuntu question Turned down the brightness of my screen from full to 1/3 Other things I have heard about but have not tried for fear of frying the laptop or my linux install: Add "pcie_aspm=force" at the end of the line with "quiet splash" in /boot/grub/grub.cfg Enable ALPM, but it may already be enabled in 12.04? Enable i915 framebuffer compression Use a propietary driver for the graphics card? Turn off the graphics card? (what would happen if I relied on the internal Intel bridge?) Use TLP? Spin down the HDD more aggressively (howto, but I think laptop-mode-tools does this already) The only other thing I've noticed is that plastic just above the F5, F6 and F7 keys gets really hot. According to Jupiter my CPU temperature is only 69 celsius and the System Monitor shows CPU load at 7% so I don't think it's the CPU. Maybe it's the graphics card? Also, I've set up MongoDB and LAMP on the machine as well. When I run powertop MongoDB is high in the list, but I'm not sure if that's relevant to battery life because I'm not actually doing anything with MongoDB most of the time. Edit - Additional info as requested $ lspci -nnk | grep -iEA3 "(graphics|vga)" 00:02.0 VGA compatible controller [0300]: Intel Corporation Ivy Bridge Graphics Controller [8086:0166] (rev 09) Subsystem: Dell Device [1028:057f] Kernel driver in use: i915 Kernel modules: i915 -- 02:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI Thames [Radeon 7500M/7600M Series] [1002:6841] Subsystem: Dell Device [1028:057f] Kernel driver in use: radeon Kernel modules: radeon

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