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• Online & Offline in Web Chat Application

  - by Mohammed Safeer

  I stuck amidst developing a chat web application using php for client side app. I used comet for chat application. And use technique of updating database when someone logout. Thus display offline on other side user. My problem is if someone close browser without logout, how the other side user know the person goes offline. How can i set online and offline icon in a php webchat application, when someone close chat window without logout? Is web sockets in php solve this problem? welcome all suggestions.

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• Why does update-notifier contains system-crash-notification?

  - by int_ua

  I just had "System Program Problem Detected" window appearing several times before user session even started (I have KDM with autologin to locked session). I traced it with xprop to being /usr/lib/update-notifier/system-crash-notification which is binary (while I expected it to be some script) and belongs to update-notifier package (while I expected it to be somewhere from apport*). P.S. Clicking on Report problem... button didn't do anything. $ dpkg -s update-notifier | grep Version Version: 0.147 $ dpkg -L update-notifier | grep system-crash /usr/lib/update-notifier/system-crash-notification $ grep RELEASE /etc/lsb-release DISTRIB_RELEASE=13.10

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• Sales Manager: "Why is time-estimation so complex?"

  - by Tim

  A few days ago a sales manager asked me that question. But at this moment I didn't know a answer which he can understand. He isn't a programmer! At the moment I work on a product which is over 8 years old. Nobody thought about architecture or evolvability. I have a swamp of code in front of me every day which is not tested. Because of that, time estimates are very difficult for me. How I can describe that problem to an salesman? Not only my swamp-code-problem, but general!

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• I'm not sure if this is a valid Ubuntu bug to file

  - by Ian Hincks

  I was in the process of filing an bug on Launchpad, but I had second thoughts because there were so many threatening warnings of the effect, "Don't file a bug report unless you're sure it's a bug, and you should really provide a package name". The problem I have, and I've had it for years, is the following: When I'm installing Ubuntu, it asks me to type in my location before it asks me what my keyboard layout is. Using a QWERTY keyboard but with the buttons popped of and in the Dvorak order, this is annoying, because it is assumes I am using a QWERTY keyboard, and so I have to guess at where all the QWERTY keys are to spell my city's name. It seems like it would make more sense to switch the order of these two questions. (I'll be the first person to admit that this is a very minor problem that has probably wasted less than 2 minutes of my life in total -- but it's the principle of the thing :p) So my question is: is this order there for a particular reason, and if it isn't, is it appropriate to file it as a bug, and under which package name?

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• "sr0" I/O read boot error in Xubuntu 12.10

  - by Entropicurity

  Just recently upgraded Xubuntu 12.10 after having installed 12.04 originally. Ever since that happened, any time I inserted a disk into my DVD/CD reader/writer I would end up getting a number of error messages from my DVD player/Audio player softer, typically with any of them either crashing or returning a GStreamer backend error. So doing some research I tried to mount it manually, and it typically returned the error messages you'll see below: (using the dmesg | grep "sr0" command) [17545.435584] end_request: I/O error, dev sr0, sector 0 [17545.492968] sr 3:0:0:0: >[sr0] [17545.492981] sr 3:0:0:0: >[sr0] [17545.492992] sr 3:0:0:0: >[sr0] [17545.493003] sr 3:0:0:0: >[sr0] CDB: [17545.493020] end_request: I/O error, dev sr0, sector 0 [17545.493058] EXT3-fs (sr0): error: unable to read superblock [17545.553224] sr 3:0:0:0: >[sr0] [17545.553237] sr 3:0:0:0: >[sr0] [17545.553247] sr 3:0:0:0: >[sr0] [17545.553258] sr 3:0:0:0: >[sr0] CDB: [17545.553275] end_request: I/O error, dev sr0, sector 0 [17545.553312] EXT4-fs (sr0): unable to read superblock [17545.611482] sr 3:0:0:0: >[sr0] [17545.611494] sr 3:0:0:0: >[sr0] [17545.611504] sr 3:0:0:0: >[sr0] [17545.611514] sr 3:0:0:0: >[sr0] CDB: [17545.611531] end_request: I/O error, dev sr0, sector 0 [17545.611568] FAT-fs (sr0): unable to read boot sector When I grepped this, the number of error messages just seemed to spill all over the screen, and typically all revolve around the I/O error. I then went into VLC and tried to run the stuff through there, but for some reason it won't read with the default devices. Instead I have to manually input sr0 into each of the /dev/ references and it will play just fine, until I exit out of the program, at which point I have to re-input everything. I have already installed all the media dependencies, both open source and restricted, through the software center. I just found this strange, as out of the box 12.04 there wasn't any problem what so ever. At this point, it could be that all my audio CD's are not in a format that is familiar with the OS (I've read in some places that EXTF4 has issues with this) but I don't see how that could be a problem when the above error messages even tested to see if it is EXT3 as well? I've tried my best to troubleshoot this up till now using existing topics, but it seems that this is a regular problem with a multitude of varying factors that incorporate into it, including but not limited to read/write problems with the format of the CD and right protection. Is there something integral that I am missing?

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• Emailing Interviewer after interview regarding technical solution

  - by Raghav Shankar

  I had an interview yesterday where I was given a programming problem and I was asked to figure the optimal solution for it. I gave a solution that worked in linear time, but used 2 loops (not inner loops). At the end of the interview, the interviewer saw I was interested in solving the problem, so he said the optimal solution uses only one loop and has linear complexity and at the end of the interview I had asked for his card and he gave one to me. I think I might have figured out a solution and I was wondering if it's alright to email the recruiter thanking him for his time and also mentioning about the solution I had figured out?

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• Increase the size of a memory mapped file

  - by sandun dhammika

  I am maintaning a memory mapped file to store my tree like datastructure. When I'm updating the datastructure ,I got this problem. The file is limited on it's size and can't be too long or too small. I have a methods like void mapfile_insert_record(RECORD* /* record*/); void mapfile_modify_record(RECORD* /* record*/); Both operations could lead to exceed the space which is free on memory file. How do I overcome this? What strategy I should use. calculate whether it requires to exceed the file as a pre-condition on both methods. Dynamically exceed it , for a example manage a timer and constantly polling file for it's free avaliable size and then automatically extend it. Any ideas or patterns to overcome this problem?

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• Ubuntu does not work with Nvidia drivers, gives random squares after logging in

  - by jimbo

  I tried installing both with wubi and by booting from a usb drive. After I tried both it was the same. Ubuntu tried to login, but after a while, a weird pattern with squarely shapes appeared. At one point, after using recovery mode and then the low graphics one (i don't remember how it was called exactly) i managed to get in. It still didn't display at correct resolution, and the mouse was invisible at times. However, after rebooting once, because i tried downloading the nvidia drivers, i didn't manage to get in again, so i have the same problem... I have no idea what to try to become unstuck. The main problem is that after the login, ubuntu crashes, with a screen full of randomly coloured squares. Should I just give up?

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• Examples of Liskov Substitution

  - by james lewis

  I'm facilitating a session next week on the Liskov Substitution Principle and I was wondering if anyone had any examples of violations 'from the trenches'? I'm looking for something other than uncle Bob's rectangle - square problem and the persistent set problem he talks about in A-PPP (although that is a great example). So far I'm using the example of a (very simple) List and an IndexedList as the 'correct' use of inheritance. And the addition of a Set to this hierarchy as a violation (as a Set is distinct; strengthening the pre condition of the Add method). I've also taken this great example and it's solution from this question Both those examples are great but I'm looking for something more subtle and harder to spot. So far I've come up with nothing so if you've got a great, subtle example post it up. Also, any metaphors you've come across that helped you understand LSP would be really useful too.

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• 12.04 Dual Monitor Configuration changes to "Mirrored" automatically

  - by Josef

  After installing 12.04 on my Samsung X120 Notebook (with Intel GMA 4500 internal graphics card) i have a Problem with the configuration off my 2nd monitor. Its a 22" with 1680 * 1050 Pixel connected via HDMI. I use the display configuration and set internal display=off and external display=main display. That works fine. After rebooting i still have that configuration, but after a while (often when i press a button on the keyboard), the configuration automatically changes to "Mirror Screen" and the internal display switches on. Both displays then have a bad resolution. When i do the manual display configuration again, everything is fine for the duration of that session. What could be the problem, that this display configuration gets lost / resets?

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• Missing Indexes DMV Report, 3 billion Impact!

  - by Tara Kizer

  We’ve been having some major performance issues with one of the applications that I support.  The database is on SQL Server 2005 and is about 150GB in size.  We’ve identified a couple of issues already on the database side.  The first issue is that some query (or maybe several queries) is getting a bad execution plan at some point in time during the day.  When it occurs, database performance comes to a grinding halt.  We know it’s a bad execution plan as running DBCC FREEPROCCACHE immediately resolves the problem system-wide.  As we have not yet identified the problematic query, we’ve put a temporary solution in place that frees the procedure cache on an hourly basis via a SQL Agent job.  This is not ideal, but it is getting us through the day without a major problem.  We are actively working on identifying the problematic query and hope to disable the SQL Agent job soon. Earlier this week, we had a major slowdown for one of the processes of this application.  I was unable to find any database performance issues, but I continued to investigate it.  One of things that I typically do when investigating database performance issues is run the “Missing Indexes DMV Report” (that’s what I call it at least).  When analyzing the output of that report, I immediately dismiss anything under 1 million “Impact” as I want to target the “low-hanging fruit” initially.  When I ran the report earlier this week, I was shocked to find a suggested index with an impact of over 3 billion! Do I win a prize for the highest impact?  Has anyone seen a value higher than mine?  My exact value was 3154284120.67765. The performance issue from earlier this week ended up being an application problem, but it also brought to light a much needed index.  I had previously seen this index come up in that report but always with a much lower impact.  I had never considered it as the index’s selectivity is very low.  It’s a composite index with three columns.  The first column is not selective, the first two columns are not selective, and the three columns together are not selective.  In fact, no matter how I order it, the index will not be selective at all.  I briefly discussed this with Kimberly Tripp, and she said that this was okay for covering indexes.  Selectivity is irrelevant for a covering index.  She indicated that she’s even created indexes with gender as the first column in the index.  I’ve got lots to learn still!

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• WPF: Reloading app parts to handle persistence as well as memory management.

  - by Ingó Vals

  I created a app using Microsoft's WPF. It mostly handles data reading and input as well as associating relations between data within specific parameters. As a total beginner I made some bad design decision ( not so much decisions as using the first thing I got to work ) but now understanding WPF better I'm getting the urge to refactor my code with better design principles. I had several problems but I guess each deserves it's own question for clarity. Here I'm asking for proper ways to handle the data itself. In the original I wrapped each row in a object when fetched from database ( using LINQ to SQL ) somewhat like Active Record just not active or persistence (each app instance had it's own data handling part). The app has subunits handling different aspects. However as it was setup it loaded everything when started. This creates several problems, for example often it wouldn't be neccesary to load a part unless we were specifically going to work with that part so I wan't some form of lazy loading. Also there was problem with inner persistance because you might create a new object/row in one aspect and perhaps set relation between it and different object but the new object wouldn't appear until the program was restarted. Persistance between instances of the app won't be huge problem because of the small amount of people using the program. While I could solve this now using dirty tricks I would rather refactor the program and do it elegantly, Now the question is how. I know there are several ways and a few come to mind: 1) Each aspect of the program is it's own UserControl that get's reloaded/instanced everytime you navigate to it. This ensures you only load up the data you need and you get some persistancy. DB server located on same LAN and tables are small so that shouldn't be a big problem. Minor drawback is that you would have to remember the state of each aspect so you wouldn't always start at beginners square. 2) Having a ViewModel type object at the base level of the app with lazy loading and some kind of timeout. I would then propegate this object down the visual tree to ensure every aspect is getting it's data from the same instance 3) Semi active record data layer with static load methods. 4) Some other idea What in your opinion is the most practical way in WPF, what does MVVM assume?

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• Secret of SQL Trace Duration Column

  - by Dan Guzman

  Why would a trace of long-running queries not show all queries that exceeded the specified duration filter?  We have a server-side SQL Trace that includes RPC:Completed and SQL:BatchCompleted events with a filter on Duration >= 100000.  Nearly all of the queries on this busy OLTP server run in under this 100 millisecond threshold so any that appear in the trace are candidates for root cause analysis and/or performance tuning opportunities. After an application experienced query timeouts, the DBA looked at the trace data to corroborate the problem.  Surprisingly, he found no long-running queries in the trace from the application that experienced the timeouts even though the application’s error log clearly showed detail of the problem (query text, duration, start time, etc.).  The trace did show, however, that there were hundreds of other long-running queries from different applications during the problem timeframe.  We later determined those queries were blocked by a large UPDATE query against a critical table that was inadvertently run during this busy period. So why didn’t the trace include all of the long-running queries?  The reason is because the SQL Trace event duration doesn’t include the time a request was queued while awaiting a worker thread.  Remember that the server was under considerable stress at the time due to the severe blocking episode.  Most of the worker threads were in use by blocked queries and new requests were queued awaiting a worker to free up (a DMV query on the DAC connection will show this queuing: “SELECT scheduler_id, work_queue_count FROM sys.dm_os_schedulers;”).  Technically, those queued requests had not started.  As worker threads became available, queries were dequeued and completed quickly.  These weren’t included in the trace because the duration was under the 100ms duration filter.  The duration reflected the time it took to actually run the query but didn’t include the time queued waiting for a worker thread. The important point here is that duration is not end-to-end response time.  Duration of RPC:Completed and SQL:BatchCompleted events doesn’t include time before a worker thread is assigned nor does it include the time required to return the last result buffer to the client.  In other words, duration only includes time after the worker thread is assigned until the last buffer is filled.  But be aware that duration does include the time need to return intermediate result set buffers back to the client, which is a factor when large query results are returned.  Clients that are slow in consuming results sets can increase the duration value reported by the trace “completed” events.

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• Flash doesn't work any more on 10.04

  - by Béné

  I have a very strange problem with flash on my 10.04 system. (An update to 12.04 is not an option, because the system is just too old and slow.) After a recent update flash has just stopped working altogether. Youtube just shows a white square, vimeo a black one. After a 10.04 reinstall the problem stays the same. Not even chrome displays flash content, just a message that shockwave flash could not be loaded. 'ubuntu-restricted-extras' 'flashplugin-nonfree' and 'flashplugin-installer' are all installed in version 11.2.202.238ubuntu0.10.04.1.

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• Apple Developer Enterprise Program?

  - by Gnial0id

  I'm building an iOS application for a client (not an enterprise but non-profit association with under than 500 employess), distributed in a free version and a "paid" one. The free version will be available with iTunes/AppStore, no problem with that. But about the paid one... the distribution my client wants is different. They want to distribute it to their clients as a bonus in their subscription, and so, to control this distribution. The first answer would be "iOS Developer Enterprise Program", but it's not an enterprise and have less than 500 employees. Will the fact that my client will distribute the app' with a subscription be a problem ? I spend a lot of time to read documentation, but it is not very clear. I'm a bit lost, I admit it. Any help would grateful.

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• 3D Studio Max biped restrictions?

  - by meds

  I have a stock biped character in 3D studio max which has a jump animation. The problem I have with the jump animation is that there is actual y offset happening inside it which makes it awkward to play while the character is jumping since it's not only jumping in the game world but the jump animation is adding its own height offset. I'm tryuing to remove the jump animations height offset, so far I've found the root node and deleted all its key frames which has helped a bit. The problem I'm having now is that the character still has some height offset and if I try to lower it it has a fake 'ground' that isn't at 0 and the limbs sort of bend on the imaginary floor, si there a way to remove this restriction just for the jump animation? Here's what I mean: http://i.imgur.com/qoWIR.png Any idea for a fix? I'm using Unity 3D if that opens any other possibilities...

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• Strange GTK3 issue with Audacious and Evince (Document Viewer)

  - by Sman789

  I find that, in some GTK3 apps such as Audacious and Evince (Document Viewer), parts of the UI are pure black, which looks ugly and out-of-place. It is not intentional, as the screenshots on both websites show the app looking different. I only have this issue with the Adwaita GTK theme, but since it comes with Gnome 3 and is the main theme these apps are designed for, I'm guessing the problem is not simply the theme having some bug (though the Ubuntu package might). I have had this issue on two laptops now, running both Ubuntu 12.04 and Xubunu 12.10 with Gnome Shell and Adwaita. The screenshots below show the problem: Audcious's is visible in the search area around the text box, and behind the playlist tabs, and Evince's is visible in more or less the same position and around the document itself. Compare this from the Audacious homepage: With this image from my system: And Evince too:

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• Monitor blinking

  - by Shark

  Hi I have Ubuntu 10.04, my laptop is ASUS k50ij, intel duo t3000, 2gb ram, 320 HDD, intel gma 4500M video card. My problem is that a couple days ago my monitor had start blinking for a few seconds. Then it stops and begins the same behaviour let's say in next 2 hours. What am i missing here? Another funny problem is that when i give more or less brightness to monitor the pop up window shows and giving "Power information: Laptop battery is charged". When my brightness is lower the blinking increases and vice versa. thx for help

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• Facebook and Gmail stop working after 10 minutes

  - by Julia

  I have problem with facebook and gmail only: It works fine and lets me log in, view photos and videos, read new messages, etc. But after 5-10 minuets it doesn't load at all This webpage is not available. The webpage at http://www.facebook.com/ might be temporarily down or it may have moved permanently to a new web address. More information on this error Below is the original error message Error 101 (net::ERR_CONNECTION_RESET): Unknown error After deleting cookies this problem disappears for 5-10 minuets, then I get the same error. It happens with Google Chrome and Firefox. Ping works fine. I have checked System-Preferences-Network Proxy it sets on Default - "Direct Internet Connection". Then I have run test (chrome://net-internals/#tests) and got some FAIL results Use system proxy settings Disable IPv6 host resolving Probe for IPv6 host resolving IPv6 is disabled.

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• Dell Inspiron touchpad not working

  - by Bobby

  I own a Dell Inspiron on which I installed 12.04 on. Everything was working great up until a couple of weeks ago when the Touchpad stopped working. It doesn't show up in mouse/touchpad settings either. I was wondering if anyone has had the same problem with 12.04 and was able to fix it. I am a noob when it comes to computer code and stuff like that, so please try to keep the answer noob proof. Also, does anyone know if the guys behind Ubuntu will have an update to fix this problem?

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• Detecting if an object is following a path

  - by justin.m.chase

  I am attempting to take GPS data and track it on a map and see if it follows a given path. I have the path as a set of points and the GPS data streams in as a similar set of points. I am attempting to track the progression of the current position across the path and I am wondering if there are any well known algorithms for this. I have come up with my own that works ok but it is a complex enough problem that I would like to minimize the amount of re-inventing of the wheel that I do. What approach or algorithm would you recommend taking for this problem?

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• creating the nodes for path finding during run time - more like path making and more

  - by bigbadbabybear

  i'm making my 1st game. i'm using javascript as i currently want to learn to make games without needing to learn another language but this is more of a general game dev question its a 2d turn-based tile/grid game. you can check it here http://www.patinterotest.tk/ it creates a movable area when you hover a player and it implements the A* algo for moving the player. The Problem: i want to make the 'dynamic movable area creation' already implement a limited number of steps for a player. The Questions: what is a good way to do this? is there another algorithm to use for this? the A* algorithm needs a start and destination, with what i want to do i don't have a destination or should i just limit the iteration of the A* algo to the steps variable? hopefully you understand the problem & questions easily

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• Using machine learning to aim mirrors in a solar array?

  - by Buttons840

  I've been thinking about solar collectors where several independent mirrors to focus the light on a solar collector, similar to the following design from Energy Innovations. Because there will be flaws in the assembly of this solar array, I am proceeding with the following assumptions (or lack thereof): The software knows the "position" of each mirror, but doesn't know how this position relates to the real world or to other mirrors. This will account for poor mirror calibration or other environmental factors which may effect one mirror but not the others. If a mirror moves 10 units in one direction, and then 10 units in the opposite direction, it will end up where it originally started. I would like to use machine learning to position the mirrors correctly and focus the light on the collector. I expect I would approach this as an optimization problem, optimizing the mirror positions to maximize the heat inside the collector and the power output. The problem is finding a small target in a noisy high-dimensional space (considering each mirror has 2 axis of rotation). Some of the problems I anticipate are: cloudy days, even if you stumble upon the perfect mirror alignment, it might be cloudy at the time noisy sensor data the sun is a moving target, it moves along a path, and follows a different path every day - although you could calculate the exact position of the sun at any time, you wouldn't know how that position relates to your mirrors My question isn't about the solar array, but possible machine learning techniques that would help in this "small target in a noisy high dimensional-space" problem. I mentioned the solar array because it was the catalyst for this question and a good example. What machine learning techniques can find such a small target in a noisy high-dimensional space? EDIT: A few additional thoughts: Yes, you can calculate the suns position in the real world, but you don't know how the mirrors position is related to the real world (unless you've learned it somehow). You might know the suns azimuth is 220 degrees, and the suns elevation is 60 degrees, and you might know a mirror is at position (-20, 42); now tell me, is that mirror correctly aligned with the sun? You don't know. Lets assume you have some very sophisticated heat measurements, and you know "with this heat level, there must be 2 mirrors correctly aligned". Now the question is, which two mirrors (out of 25 or more) are correctly aligned? One solution I considered was to approximate the correct "alignment function" using a neural network which would take the suns azimuth and elevation as input and output a large array with 2 values for each mirror which correspond to the 2 axis of each mirror. I'm not sure what the best training method is though.

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• How to set up a one-man research in the difference between BDD and Waterfall?

  - by Martijn van der Maas

  Earlier, I asked a question about how to measure the quality of a project. The outcome of that question was that the quality of the project can be divided into two parts: Internal quality (code quality, measurable by code quality metrics) External quality (Acceptance test, how well the software meets the requirements) So based on that, I want to set up some research and validate the outcome of the project. The problem is, I will conduct this research on my own, so it's not possible to run the project once in BDD style and the other one in waterfall by myself. It's also not possible to compare BDD and waterfall projects on a larger scale, due to the fact that there are not enough BDD projects that can be measured because of the age of BDD. So, my question is: did anybody face this problem? How could I execute my experiment in such a way that it is of scientific value?

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• Seek Steering Behavior with Target Direction for Group of Fighters

  - by SebastianStehle

  I am implementing steering algorithms with group management for spaceships (fighters). I select a leader and assign the target positions for the other spaceships based on the target position of the leader and an offset. This works well. But when my spaceships arrive they all have a different direction. I want them to keep to look in the same direction (target - start). I also want to combine this behavior with a minimum turning radius that is based on the speed. The only idea I have is to calculate a path for each spaceship with an point before the target position, so the ships have some time left to turn into the right position. But I dont know if this is a good idea. I guess there will be a lot of rare cases where this can cause a problem. So the question is, if anybody knows how to solve this problem and has some (simple code) or pseudocode for me or at least some good explanation.

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