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• Pandaboard crash on startup or freeze after minutes

  - by Meach

  I just received my Pandaboard ES (rev B) and I am having trouble after installing ubuntu-omap4-addons. Once I copied the image ubuntu-12.04-preinstalled-desktop-armhf+omap4.img on my sd card and boot the pandaboard with it, I run the following commands: sudo add-apt-repository ppa:tiomap-dev/release sudo apt-get update sudo apt-get dist-upgrade sudo apt-get install ubuntu-omap4-extras At the end of the installation of ubuntu-omap4-extras, Ubuntu tells me that a problem occurs when the console displays: ldconfig deferred processing now taking place Clicking on "report the problem" tell me that the problem concerns pvr-omap4-dkms. I read somewhere that this can happen and it is better to reinstall pvr-omap4-dkms. Which I am doing by running: sudo apt-get install --reinstall pvr-omap4-dkms I reboot. Then the board has sometimes difficulties to start Ubuntu: it freezes during the loading page, only action I can do is unplugging the board to start it again. Some other times, Ubuntu load successfully but then freeze at another random time, in the range 20 - 40 minutes. I searched on internet for similar bug and found this: https://bugs.launchpad.net/ubuntu/+source/linux-ti-omap4/+bug/971091 So I typed this in: update-rc.d ondemand disable apt-get -y install cpufrequtils echo 'ENABLE="true" GOVERNOR="performance" MAX_SPEED="0" MIN_SPEED="0"' > /etc/default/cpufrequtils cpufreq-set -r -g performance reboot But it doesn't seems to fix the bug. Another detail: on startup, before the loading screen of Ubuntu (when there is the two penguins displayed :)), it shows this: [0.297271] CPU1: Unknown IPI message 0x1 [0.308990] omap_hwmod: mcpdm: _wait_target_ready error: -16 [0.354705] omap_mux_get_by_name: Could not find signal uart1_cts.uart1_cts [0.354766] omap_hwmod_mux_init: Could not allocate device mux entry [2.107086] thermal_get_slope:Getting slope is not supported for domain gpu [2.107116] thermal_get_offset:Getting offset is not supported for domain gpu [2.107299] stm_fw: vendor driver stm_ti1.0 registered [8.725555] OMAPRPC: Registration of OMAPRPC rpmsg service returned 0! debug=0 Any idea what can be wrong? I am not that good with Ubuntu so any help will be appreciated. Cheers! Meach

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• Handling exceptions raised in observers

  - by sparky

  I have a Rails (2.3.5) application where there are many groups, and each Group has_many People. I have a Group edit form where users can create new people. When a new person is created, they are sent an email (the email address is user entered on the form). This is accomplished with an observer on the Person model. The problem comes when ActionMailer throws an exception - for example if the domain does not exist. Clearly that cannot be weeded out with a validation. There would seem to be 2 ways to deal with this: A begin...rescue...end block in the observer around the mailer. The problem with this is that the only way to pass any feedback to the user would be to set a global variable - as the observer is out of the MVC flow, I can't even set a flash[:error] there. A rescue_from in the Groups controller. This works fine, but has 2 problems. Firstly, there is no way to know which person threw the exception (all I can get is the 503 exception, no way to know which person caused the problem). This would be useful information to be able to pass back to the user - at the moment, there is no way for me to let them know which email address is the problem - at the moment, I just have to chuck the lot back at them, and issue an unhelpful message saying that one of them is not correct. Secondly (and to a certain extent this make the first point moot) it seems that it is necessary to call a render in the rescue_from, or it dies with a rather bizarre "can't convert Array into String" error from webbrick, with no stack trace & nothing in the log. Thus, I have to throw it back to the user when I come across the first error and have to stop processing the rest of the emails. Neither of the solutions are optimal. It would seem that the only way to get Rails to do what I want is option 1, and loathsome global variables. This would also rely on Rails being single threaded. Can anyone suggest a better solution to this problem?

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• How to handle the different frame rate on different devices?

  - by Fenwick

  I am not quite sure how frame per second works on a web page. I have a Canvas game that involves in moving an image from point A to B, and measuring the time elapsed. The code can be as simple as: var timeStamp = Date.now(); function update(){ obj.y += obj.speed; text = "Time: "+ (Date.now() - timeStamp) + "ms"; } The function update() is called every frame. The problem is that the time elapsed is different from device to device. It is pretty short on my PC, but get longer on my iPad, and is much longer on my cell phone. I thought it is because the FPS is smaller on mobile devices, so instead of calling update() every frame, I call it every 1ms by using a setInterval. But this does not solve the problem. In my understanding, the function for setInterval is invoked based on the increment in system time, other than frame rate, so it should fix the problem. Am I missing anything here? If the setInterval function is called based on FPS, is there any way to get around with the FPS difference across devices? On a side note, I have sort of a "water simulator" on the same canvas. It involves in redrawing about 60 objects which can be 600x600 pixels for every frame, so it could be a frame rate killer. I am using Phaser.js but not really using much of its functionalities, if that helps.

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• Cron prepending filename to script output

  - by Caitifty

  I'm having an issue with unwanted lines being added to files output by a cron job. I have a script in /etc/cron.hourly which selects some data from a mysql database and saves it in a text file in /var/www. When I run the script as root, it does exactly what I expect it to do. When the script is executed by cron, it creates the same file, but prepends the following three lines at the top of the output file: :::::::::::::: /var/www/outputfilename :::::::::::::: I can't for the life of me work out how to stop this unwanted behavior. The line in /etc/crontab for cron.hourly is the default "44 * * * * root cd / && run-parts --report /etc/cron.hourly". If I use su to change to being root and do "cd / && run-parts --report /etc/cron.hourly" the script runs as expected and the output doesn't have the mysterious additional 3 lines. I've also tried removing the --report flag from the run-parts command in case that was somehow connected, but no joy. Finally, perusing the cron log output in /var/log/syslog just says cron.hourly ran without giving any additional information. Any suggestions on solving this weird problem most welcome..

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• Can Dungeons & Dragons Make You More Successful? [Video]

  - by Jason Fitzpatrick

  Dungeons & Dragons gets a bit of a bad rap in popular culture, but in this video treatise from Idea Channel, they propose that Dungeons & Dragons wires players for success. There are some deeply ingrained stereotypes about Dungeons & Dragons, and those stereotypes usually begin and end with people shouting “NERD!!!” But the reality of the D&D universe is a whole lot more complex. Rather than being an escape from reality, D&D is actually a way to enhance some important real life skillz! It’s a chance to learn problem solving, visualization, interaction, organization, people management… the list could go on and on. Plus, there are some very famous non-nerds who have declared an affinity for D&D, so best stop criticizing and join in if you want to be a successful at the game of life. While we’re trying not to let our love of all things gaming cloud our judgement, we’re finding it difficult to disagree with the premise that open-ended play fosters creative and adaptive thinking. Can Dungeons & Dragons Make You A Confident & Successful Person? [via Boing Boing] HTG Explains: What is the Windows Page File and Should You Disable It? How To Get a Better Wireless Signal and Reduce Wireless Network Interference How To Troubleshoot Internet Connection Problems

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• Source code not matching uploaded HTML file

  - by benhowdle89

  I'm not sure if this is the right place to ask but i'm having a hugely frustrating problem with Coda and my website (i'm not sure which one is causing the issue) I'm using Coda to make changes to my website, Coda uses built in FTP to save changes to your web page. So when you hit Save, it uploads the new file. I've been using Coda for months and never had a problem until now. I am making changes in the html of my index.php and hitting save, it's successfully uploading the file but no changes are reflected in the source code in ANY browser. I even logged into cPanel on my website, ie. www.example.com:2082 and looked at the file - the changes have been made successfully. But the actual webpage in browser's source code, no changes?? I have tried adding which made no difference. Interestingly i make changes to style.css and the changes are instant. I have emptied the cache on all of my browsers but i'm still having an issue. Does this sound like a Coda problem or has anyone heard of such a thing?

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• How do I stop video tearing? (Nvidia prop driver, non-compositing window manager)

  - by Chan-Ho Suh

  I have that problem which seemingly afflicts many using the proprietary Nvidia driver: Video tearing: fine horizontal lines (usually near the top of my display) when there is a lot of panning or action in the video. (Note: switching back to the default nouveau driver is not an option, as its seemingly nonexistent power-management drains my battery several times faster) I've tried Totem, Parole, and VLC, and tearing occurs with all of them. The best result has been to use X11 output in VLC, but there is still tearing with relatively moderate action. Hardware: MacBook Air 3,2 -- which has an Nvidia GeForce 320M. There are two common fixes for tearing with Nvidia prop drivers: Turn off compositing, since Nvidia proprietary drivers don't usually play nice with compositing window managers on Linux (Compiz is an exception I'm aware of). But I use an extremely lightweight window manager (Awesome window manager) which is not even capable of compositing (or any cool effects). I also have this problem in Xfce, where I have compositing disabled. Enabling sync to VBlank. To enable this, I set the option in nvidia-settings and then autostart it as nvidia-settings -l with my other autostart programs. This seems to work, because when I run glxgears, I get: $ glxgears Running synchronized to the vertical refresh. The framerate should be approximately the same as the monitor refresh rate. 303 frames in 5.0 seconds = 60.500 FPS 300 frames in 5.0 seconds = 59.992 FPS And when I check the refresh rate using nvidia-settings: $ nvidia-settings -q RefreshRate Attribute 'RefreshRate' (wampum:0.0; display device: DFP-2): 60.00 Hz. All this suggests sync to VBlank is enabled. As I understand it, this is precisely designed to stop tearing, and a lot of people's problem is even getting something like glxgears to output the correct info. I don't understand why it's not working for me. xorg.conf: http://paste.ubuntu.com/992056/ Example of observed tearing::

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• What is the best way to handle dynamic content?

  - by user1561753

  So we run a site where there are elements of the interface that could potentially be changed at any moment in the backend. Specifically we run a web service where certain functions are loaded dynamically. However, there are times where we remove certian functions and we want the experience to be as seamless for the user as possible. Now we've considered a few methods of solving this Ping the server every few seconds. If the functions are outdated/no longer available refresh the users page. While this would work the best, I feel like having that much IO can't be too good When the user clicks a function, if it's outdated/no longer available, alert them in the response and refresh the page. This would also work fairly well. I guess I'm more wondering how web apps like Google Docs work where you have content that has to be synced up across multiple users and that isn't more than a few seconds outdated Sorry if this isn't the best place to ask this. I figured this was more of a site architecture question and that this might be the place to ask it over SO.

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• Lenovo Y460 Intel Driver Secondary Display Flickering

  - by ultimatebuster

  This is a part of the massive dump of problems I'm encountering with my Lenovo Y460 and Ubuntu. Problem: ATI PowerXpress doesn't really work. Doesn't work as I have to use the open source driver with hacks. Turned off ATI card at boot Details on how I accomplished that: http://ubuntuforums.org/showthread.php?p=10955831#post10955831 Installing the ATI drivers results in a failure of the intel drivers to work with Ubuntu Class (all animations have to turned off). Anyway to fix this problem to allow switchable graphics to work? The problem above has been fixed by FGLRX (Catalyst 11.6) is it compatible with kernel 2.6.39? However, there's another issue. If I connect my secondary monitor (VGA 17'') while using the Intel driver, I would not be able to use that screen as there's flickering and tearing, making the screen blurry and usable. Here's the fglrxinfo: $ fglrxinfo display: :0.0 screen: 0 OpenGL vendor string: Tungsten Graphics, Inc OpenGL renderer string: Mesa DRI Intel(R) Ironlake Mobile GEM 20100330 DEVELOPMENT OpenGL version string: 1.4 (2.1 Mesa 7.10.2) Any fixes for that? Potential related bug report on launchpad: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/750259 However I can't confirm because the video showing that is much more dramatic than what I have, mine are tiny flickering that won't be captured by video cameras as I've tried, but enough to make it blurry for humans.

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• SSD on USB 3.0 doesnt always mount

  - by juergen

  I would like to ask you for some support for this issue. The SSD I use is apparently slightly damaged. Atm it shows this popular Corsair Series 3 problem. symptom: the disk is working for some minutes and then just suddenly stops. Two months ago it worked like a charm. This was my boot device in these days. So now I still need to copy some data out of the device which leads me to my question. Usually the SSD is working again for some minutes, when i unplug and replug its power. It gets detected by the system again and I can continue my backup. The problem on Ubuntu is, that it is not recognized again after two or three replugs. I have to reboot to bring it back. To specify this situation: when i unplug and replug my USB mouse before i reboot it is not recognized as well. So something seems to be wrong with the system also. my question: how do i fix this rebooting issue? I will post all the logs you need to analyse. The problem doesnt depend on the interface. I tried USB3.0, 2.0 and Sata already. Thank you! cheers my system: Ubuntu 11.10, Gigabyte G41MT-S2P, Intel E6750 Corsair Force Series 2 - F120, Digitus USB 3.0 Adapter, USB 3.0 interface card

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• Choppy USB mice on just one of USB ports

  - by user20532

  I've got Lenovo b560 laptop with latest, properly updated Kubuntu on it (11.04 natty, kernel 2.6.38-8-generic). It has three USB2.0 ports onboard. I usually plug a mouse into one of them (I've got 3 different mice - in office, at home and for when on the go). Sometimes, usually after laptop awakening from sleep, the mouse still works but cursor movements are choppy, as if the processor was extremely loaded (it's usually not). I found that if I re-plug the mouse cord into the other USB port, it works just fine. If I plug it back to problematic port, it is still choppy and remains choppy until next boot. Of course I want my mice to always work fine. Problem is: I cannot reproduce this behavior for sure, it happens sporadically but regularly. I use different USB ports (problem has ever happened on each of them since), I use different mice (each has failed me this way at least once), I cannot generally find what exactly is going wrong and why plugging to different port fixes the mouse instantly. So I'd like to hear at least clues where to look at, what to try to identify my problem. A bit of update: while beginning this post, I had the issue once again. I have just replugged the mouse back to problematic port and it is not recognized at all. On the other port it works smoothly.

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• Sun Java crashing, mostly with jboss

  - by Joel

  I'm on Ubuntu 10.10. I keep having problems with Sun Java crashing on me. I mostly have it crashing on my Jboss server, but I've had it crash MANY MANY times running ANT tasks or the IntelliJ IDE. Here's what it prints: # # A fatal error has been detected by the Java Runtime Environment: # # SIGSEGV (0xb) at pc=0x00007f67e665d440, pid=21260, tid=140082772170512 # # JRE version: 6.0_22-b04 # Java VM: Java HotSpot(TM) 64-Bit Server VM (17.1-b03 mixed mode linux-amd64 ) # Problematic frame: # V [libjvm.so+0x2f2440] # # An error report file with more information is saved as: # /home/blah/blah/blah/hs_err_pid21260.log # # If you would like to submit a bug report, please visit: # http://java.sun.com/webapps/bugreport/crash.jsp # Aborted A co-worker of mine who has the same version of Ubuntu has had the same problem, but has only happened to him once. (I get this probably 2 or 3 times a day, if not more). I have another machine running Ubuntu 10.04 with Sun Java and I have yet to see this problem. 1.0.6_20 is the java version on the 10.04 machine. My machine is running 1.6.0_22. Has anyone else had this problem? Anyone know how to keep it from happening? Also: I have tried reinstalling it and I can't use OpenJDK.

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• ISA Proxy server

  - by user59931

  Have a proxy at work that runs Microsoft ISA. i used to be able to connect using 11.10 with firefox no problem at all. i could either put the settings in firefox or the settings in ubuntu network proxy settings. this would give me a connection no problem ( slow due to the work network being really lame) since i upgraded with 12.10 firefox just crashes if i have any proxy settings (manual added the proxy settings). if i connect to a diffrent network without the proxy settings it works fine and doesn't crash i tried chrome to see if that would work... simular problem. chrome doesn't crash but is so slow it just times out all the time and can take 10min for a page to load.... not really sure where to go with this? i have tried a clean install of 12.04 on 2 diffrent computers and also both tried just upgrading from 11.10. Only answer i can see at the moment is role back to 11.10 :( i have tried all sorts like turning of IPv6 to see if that would make any diffrence but no joy... really am lost now. whats weird is the repositys are also really really slow through 12.04. 50 megs took an hour to download (ISA server has Ubuntu rep servers enables without authenication). really am lost

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• Can't Log Into Ubuntu 12.04

  - by Razick

  Yesterday, after turning on Ubuntu, I logged into a Gnome session. A few minutes later, I tried switching to Unity for a change. Unfortunately, the background and my desktop icons loaded, but the system bar and launcher failed to load even after several minutes. Unity had always worked fine for me. I then tried the guest account, and it worked fine on both Unity and Gnome. However, the problem with my account got worse; I couldn't log into any desktop at all anymore. I would type in my password and press enter and it would just sit there doing nothing. The computer no longer responded in any way, so I had to hold the power button and reboot. The same problem happened repeatedly. Earlier today, I tried to get on again. I found that I hadthe same problem, when I tried to log in, the computer no longer locked up, but instead flashed a black screen with theconsole output and what seemed to be an error message before returning to the log in screen. It was to quick for me to read, about 1/4-1/2 second. I'd really appreciate some help as I have some important files that are not backed up yet. I can't transfer the files to a new account, or even make a new account because I tried taking the password off my account so now I can't authenticate from the guest to perform root functions. I'd really appreciate some help as I have some important files that are not backed up yet. Thanks.

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• Video freezes when larger than a certain size

  - by Poyan

  I have a weird problem playing video files. I have a fairly new (a few years old) graphic card that should and has played up to 1080p video files without much a lot of trouble. I seem to be having a weird issue where the video plays back fine if the window is below a certain size, but as soon as the windowsize increases, the picture freezes. The audio still plays. Usually this is mitigated by killing som applications. Especially GTK (?) apps seem to cause this lag, like having a Nautilus window open usually triggers this error for me. With hardware rendering I get the error regardless of application. I have tried enabling software rendering in VLC and that eliminates the problem (but I get other problems using software rendering, so I've avoided it). I know this is pretty fuzzy, but I'm not sure how to approach this problem. Do you have any idea? EDIT: Some more information. I have the correct and latest drivers installed. My graphics card is a Nvidia 7600 GT.

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• How do I interpolate air drag with a variable time step?

  - by Valentin Krummenacher

  So I have a little game which works with small steps, however those steps vary in time, so for example I sometimes have 10 Steps/second and then I have 20 Steps/second. This changes automatically depending on how many steps the user's computer can take. To avoid inaccurate positioning of the game's player object I use y=v0*dt+g*dt^2/2 to determine my objects y-position, where dt is the time since the last step, v0 is the velocity of my object in the beginning of my step and g is the gravity. To calculate the velocity in the end of a step I use v=v0+g*dt what also gives me correct results, independent of whether I use 2 steps with a dt of for example 20ms or one step with a dt of 40ms. Now I would like to introduce air drag. For simplicity's sake I use a=k*v^2 where a is the air drag's acceleration (I am aware that it would usually result in a force, but since I assume 1kg for my object's mass the force is the same as the resulting acceleration), k is a constant (in this case I'm using 0.001) and v is the speed. Now in an infinitely small time interval a is k multiplied by the velocity in this small time interval powered by 2. The problem is that v in the next time interval would depend on the drag of the last which again depends on the v of the last interval and so on... In other words: If I use a=k*v^2 I get different results for my position/velocity when I use 2 steps of 20ms than when I use one step of 40ms. I used to have this problem for my position too, but adding +g*dt^2/2 to the formula for my position fixed the problem since it takes into account that the position depends on the velocity which changes slightly in every infinitely small time interval. Does something like that exist for air drag too? And no, I dont mean anything like Adding air drag to a golf ball trajectory equation or similar, for that kind of method only gives correct results when all my steps are the same. (I hope you can understand my intermediate english, it's not my main language so I would like to say sorry for all the silly mistakes I might have made in my question)

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• linq to sql with nservicebus table lock issue

  - by IGoor

  I am building a system using NServiceBus and my DataLayer is using Linq 2 SQL. The system is made up of 2 services. Service1 receives messages from NSB. It will query Table1 in my database and inserts a record into Table1 If a certain condition is met a new NSB message is sent to the 2nd service Service2 will update records also in Table1 when it receives messages from Service1 and it does some other non database related work. Service2 is a long running process. The problem I am having is the moment Service2 updates a record in Table1, the table is locked. The lock seems to be in place until Service2 has completed all it is processing. i.e. The lock is not released after my datacontext is disposed. This causes the query in Service1 to timeout. Once Service2 completes processing, Service1 resumes processing again without problem. So for example Service1 code may look like: int x =0; using (DataContext db = new DataContext()) { x = (from dp in db.Table1 select dp).Count(); // this line will timeout while service2 is processing Table1 t = new Table1(); t.Data = "test"; db.Table1.InsertOnSubmit(t); db.SubmitChanges(); } if(x % 50 == 0) CallService2(); The code in service2 may look like: using (DataContext db = new DataContext()) { Table1 t = db.Table1.Where(t => t.id == myId); t.Data = "updated"; db.SubmitChanges(); } // I would have expected the lock to have been released at this point, but this is not the case. DoSomeLongRunningTasks(); // lock will be released once service2 exits I don't understand why the lock is not released when the datacontext is disposed in Service2. To get around the problem I have been calling: db.ExecuteCommand("SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED"); and this works, but I am not happy using it. I want to solve this problem properly. Has any one experienced this sort of problem before and does any one know how to solve it? Why is the lock not released after the datacontext has been disposed? Thanks in advance. p.s. sorry for the extremely long post.

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• Looking for a better Factory pattern (Java)

  - by Sam Goldberg

  After doing a rough sketch of a high level object model, I am doing iterative TDD, and letting the other objects emerge as a refactoring of the code (as it increases in complexity). (That whole approach may be a discussion/argument for another day.) In any case, I am at the point where I am looking to refactor code blocks currently in an if-else blocks into separate objects. This is because there is another another value combination which creates new set of logical sub-branches. To be more specific, this is a trading system feature, where buy orders have different behavior than sell orders. Responses to the orders have a numeric indicator field which describes some event that occurred (e.g. fill, cancel). The combination of this numeric indicator field plus whether it is a buy or sell, require different processing buy the code. Creating a family of objects to separate the code for the unique handling each of the combinations of the 2 fields seems like a good choice at this point. The way I would normally do this, is to create some Factory object which when called with the 2 relevant parameters (indicator, buysell), would return the correct subclass of the object. Some times I do this pattern with a map, which allows to look up a live instance (or constructor to use via reflection), and sometimes I just hard code the cases in the Factory class. So - for some reason this feels like not good design (e.g. one object which knows all the subclasses of an interface or parent object), and a bit clumsy. Is there a better pattern for solving this kind of problem? And if this factory method approach makes sense, can anyone suggest a nicer design?

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• Groovy Grapes in NetBeans IDE

  - by Geertjan

  The start of Groovy Grapes support in NetBeans IDE. Below you see a pure Groovy project, with the Groovy JAR and the Ivy JAR automatically on its classpath. There's also a Groovy script that makes use of a @Grab annotation. In the bottom left, in the Services window, you also see a Grape Repository browser, i.e., showing you the JARs that are currently in ".groovy/grapes". Click the images below to get a better look at them. Next, you see what happens when the project is run. The @Grab annotation automatically starts downloading the JARs that are needed and puts them into the ".groovy/grapes" folder. However, the "no suitable classloader found for grab" error message (which Google shows is a problem for lots of developers) prevents the application from running successfully: The final screenshot shows that I've put the JARs that I need onto the classpath of the project. I did that manually, hoping to learn from the NetBeans Maven project or the NetBeans Gradle project how to do that automatically. Also note that the @Grab annotation has been commented out. Now the error message about the classloader is avoided and the project runs. What needs to happen for Groovy Grapes support to be complete in NetBeans IDE: Figure out how to add the downloaded JARs to the project classpath automatically. Fix the refresh problem in the Grape Repository browser, i.e., right now the refresh doesn't happen automatically yet. Hopefully find a way to get around the grab classloader problem, i.e., it's not ideal that one needs to comment out the annotation. Let the user specify a different Grape repository, i.e., right now ".groovy/grapes" is assumed, but the user should be able to point the repository browser to something different. Maybe there should be support for multiple Grape repositories? Comments/feedback/help is welcome.

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• FP for simulation and modelling

  - by heaptobesquare

  I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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• The Start of a Blog

  - by dbradley

  So, here's my new blog up and running, who am I and what am I planning to write here?First off - here's a little about me:I'm a recent graduate from university (coming up to a year ago since I finished) studying Software Engineering on a four year course where the third year was an industrial placement. During the industrial placement I went to work for a company called Adfero in a "Technical Consultant" role as well as a junior "Information Systems Developer". Once I completed my placement I went back to complete my final year but also continued in my developer role 2/3 days a week with the company.Working part time while at uni always seems like a great idea until you get half way through the year. For me the problem was not so much having a lack of time, but rather a lack of interest in the course content having got a chance at working on real projects in a live environment. Most people who have been graduated a little while also find this - when looking back at uni work, it seem to be much more trivial from a problem solving point of view which I found to be true and I found key to uni work to actually be your ability to prove though how you talk about something that you comprehensively understand the basics.After completing uni I then returned full time to Adfero purely in the developer role which is where I've now been for almost a year and have now also taken on the title of "Information Systems Architect" where I'm working on some of the more high level design problems within the products.What I'm wanting to share on this blog is some of the interesting things I've learnt myself over the last year, the things they don't teach you in uni and pretty much anything else I find interesting! My personal favorite areas are text indexing, search and particularly good software engineering design - good design combined with good code makes the first step towards a well-written, maintainable piece of software.Hopefully I'll also be able to share a few of the products I've worked on, the mistake I've made and the software problems I've inherited from previous developers and had to heavily re-factor.

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• Is it better to specialize in a single field I like, or expand into other fields to broaden my horizons?

  - by Oak

  This is a dilemma about which I have been thinking for quite a while. I'm a graduate student and my topics of interest are programming language design, code analysis, compilation, etc. So far, this field has been very interesting and rewarding for me, so I was thinking about finding a job in that field and continuing to specialize in it. I feel like it's a relatively solid field which won't "get out of style" anytime soon. I've always thought that in such complex fields it's better to be a real expert than just another guy who superficially understand what the experts are talking about. On the other hand, I feel that by specializing this way I really limit my future option. I have always been a strong believer in multidisciplinary approaches to problems. Maybe I should go search for a general programming job in which I could gain experience in other fields, as well as occasionally apply my favorite field for solving problems. Specializing in only one or two fields can prevent me from thinking outside the box and cause stagnation. I would really like to hear more opinions about this choice. The truth is I'm already leaning towards one of the choices, so basic psychology says nothing will change my mind, but I would still love to hear some feedback.

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• How do you avoid name similarities between your classes and the native ones?

  - by Oscar

  I just ran into an "interesting problem", which I would like your opinion about: I am developing a system and for many reasons (meaning: abstraction, technology independence, etc) we create our own types for exchanging information. For instance: if there is a method which is called SendEmail and is invoked by the business logic, it way have a parameter of type OurCompany.EMailMessage, which is an object which is completely technology independent and contains only "business relevant data" (for instance, no information abut head encoding). Inside the SendEmail function, we get this information from our EMailMEssage object and create a MailMessage (this one is technolgy specific) object so it can be sent over the network. As you can already notice, our class has a very similar name to the "native" language class. The problem is: this is exactly what they are, email messages, so it is hard to find another meaningful name for them. Do you have this problem often? How do you manage it? Edit: @mgkrebbs just commented about using fully qualified names. This is our current approach, but a little bit too verbose, IMHO. I would like something cleaner, if possible.

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• Why is math taught "backwards"? [closed]

  - by Yorirou

  A friend of mine showed me a pretty practical Java example. It was a riddle. I got excited and quickly solved the problem. After it, he showed me the mathematical explanation of my solution (he proved why is it good), and it was completely clear for me. This seems like natural approach for me: solve problems, and generalize. This is very familiar to me, I do it all the time when I am programming: I write a function. When I have to write a similar function, I generalize the problem, grab the generic parts, and refactor them to a function, and solve the original problems as a specialization of the general function. At the university (or at least where I study), things work backwards. The professors shows just the highest possible level of the solutions ("cryptic" mathematical formulas). My problem is that this is too abstract for me. There is no connection of my previous knowledge (== reality in my sense), so even if I can understand it, I can't really learn it properly. Others are learning these formulas word-by-word, and get good grades, since they can write exactly the same to the test, but this is not an option for me. I am a curious person, I can learn interesting things, but I can't learn just text. My brain is for storing toughts, not strings. There are proofs for the theories, but they are also really hard to understand because of this, and in most of the cases they are omitted. What is the reason for this? I don't understand why is it a good idea to show the really high level of abstraction and then leave the practical connections (or some important ideas / practical motivations) out?

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• Make Gameobject Stand On Surface Facing Certain Direction

  - by Julian

  I want to make a biped character stand on any surface I click on. Surfaces have up vectors of any of positive or negative X,Y,Z. So imagine a cube with each face being a gameobject whose up vector pointing directly away from the cube. If my character is facing "forward" and I click on a surface which is to the left or right of me ( left or right walls), I want my character to now be standing on that surface but still be facing in the direction he initially was. If I click on a wall which is in the forward path of my character i want him to now be standing on that surface and his forward to now be what was once "up" relative to my character. Here is the code I am working with now. void Update() { if (Input.GetMouseButtonUp (0)) { RaycastHit hit; var ray = Camera.main.ScreenPointToRay(Input.mousePosition); if (Physics.Raycast(ray, out hit)) { Vector3 upVectBefore = transform.up; Vector3 forwardVectBefore = transform.forward; Quaternion rotationVectBefore = transform.rotation; Vector3 hitPosition = hit.transform.position; transform.position = hitPosition; float lookDifference = Vector3.Distance(hit.transform.up, forwardVectBefore); if(Vector3.Distance(hit.transform.up, upVectBefore) < .23) //Same normal { transform.rotation = rotationVectBefore; } else if(lookDifference > 1.412 && lookDifference <= 1.70607) //side wall { transform.up = hit.transform.up; transform.forward = forwardVectBefore; } else //head on wall { transform.up = hit.transform.up; transform.forward = upVectBefore; } } } } The first case "Same normal" works fine, however the other two do not work as I would like them to. Sometimes my character is laying down on the surface or on the wrong side of the surface. Does anyone know nice way of solving this problem?

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