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  • How to improve performance

    - by Ram
    Hi, In one of mine applications I am dealing with graphics objects. I am using open source GPC library to clip/merge two shapes. To improve accuracy I am sampling (adding multiple points between two edges) existing shapes. But before displaying back the merged shape I need to remove all the points between two edges. But I am not able to find an efficient algorithm that will remove all points between two edges which has same slope with minimum CPU utilization. Currently all points are of type PointF Any pointer on this will be a great help.

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  • Most efficient algorithm for mesh-level, optimal occlusion culling?

    - by Fredriku73
    I am new to culling. On a first glance, it seems that most occlusion culling algorithms are object-level, not examining single meshes, which would be practical for game rendering. What I am looking for is an algorithm that culls all meshes within a single object that are occluded for a given viewpoint, with high accuracy. It needs to be at least O(n log n), a naive mesh-by-mesh comparison (O(n^2)) is too slow. I notice that the Blender GUI identifies the occluded meshes for you in real-time, even if you work with large objects of 10,000+ meshes. What algorithm is used there, pray tell?

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  • Fade a color to white (increasing brightness)

    - by Jon B
    I want to make a text box in .NET "glow" yellow, and then "fade" to white (basically, by incrementally increasing the brightness). I think Stackoverflow does this after you've posted an answer. I know that increasing brightness is not all that simple (it's not just uniformly increasing/decreasing RGB), but I'm not sure how to do this. Perfect color accuracy is not important for this. I am using C#, although VB examples would be just fine, too. Edit: This is for Winforms.

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  • Bash: Check if file was modified since used in script

    - by Thomas Münz
    I need to check in a script if a file was modified since I read it (another application can modify it in between). According to bash manual there is a "-N" test which should report if a file was modified since last read. I tried it in a small script but it seems like it doesn't work. #!/bin/bash file="test.txt" echo "test" > $file cat $file; if [ -N $file ]; then echo "modified since read"; else echo "not modified since read"; fi I also tried an alternative way by touching another file and using if [ "file1" -nt "file2 ]; but this works only on a seconds accuracy which may under rare conditions not be sufficient. Is there any other bash-inbuilt solution for this problem or I do really need to use diff or md5sum?

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  • What is the best Java numerical method package?

    - by Bob Cross
    I am looking for a Java-based numerical method package that provides functionality including: Solving systems of equations using different numerical analysis algorithms. Matrix methods (e.g., inversion). Spline approximations. Probability distributions and statistical methods. In this case, "best" is defined as a package with a mature and usable API, solid performance and numerical accuracy. Edit: derick van brought up a good point in that cost is a factor. I am heavily biased in favor of free packages but others may have a different emphasis.

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  • Orbital equations, and power required to run them

    - by Adam Davis
    Due to a discussion on the SO IRC today, I'm curious about orbital mechanics, and The equations needed to solve orbital problems The computing power required to solve complex problems The question in particular is calculating when the Earth will plow into the Sun (or vice versa, depending on the frame of reference). I suspect that all the gravitational pulls within our solar system may need to be calculated, which makes me wonder what type of computer cluster is required, or can this be done on a single box? I don't have the experience to do a back of the napkin test here, but perhaps you do? Also, much thx to Gortok for the original inspiration (see comments).

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  • help with matlab and Discrete Fourier transform

    - by user504363
    Hi all I have previous experience with Matlab, but the problem that I face some problems in apply a problem in (DSP : Digital signal processing) which is not my study field, but I must finish that problems in days to complete my project. all i want is help me with method and steps of solving this problem in matlab and then I can write the code with myself. the problem is about the signal x(t) = exp(-a*t); 1) what's the Discrete Fourier transform of the sampled signal with sample rate fs 2) if a=1 and fs =1 , plot the amplitude spectrum of sampled signal 3) fix the sampling frequency at fs = 1(hz) [what's it mean ?] and plot the magnitude of the Fourier Transform of the sampled signal at various values of a thanks

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  • Programming with midi, and tuning notes to specific frequencies

    - by froggie0106
    I am working on a project in which I need to be able to generate midi notes of varying frequencies with as much accuracy as possible. I originally tried to write my program in Java, but it turns out that the sound.midi package does not support changing the tunings of notes unless the frequencies are Equal Tempered frequencies (or at least it didn't in 1.4, and I haven't been able to find evidence that this has been fixed in recent versions). I have been trying to find a more appropriate language/library to accomplish this task, but since this is my first time programming with MIDI and my need for specific tuning functionality is essential, I have been having considerable trouble finding exactly what I need. I am looking for advice from people who have experience writing MIDI programs as to what languages are useful, especially for tuning notes to specific frequencies. Any links to websites with API docs and example code would also be extremely helpful.

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  • Implementing tracing gestures on iPhone

    - by bmoeskau
    I'd like to create an iPhone app that supports tracing of arbitrary shapes using your finger (with accuracy detection). I have seen references to an Apple sample app called "GestureMatch" that supposedly implemented exactly that, but it was removed from the SDK at some point and I cannot find the source anywhere via Google. Does anyone know of a current official sample that demonstrates tracing like this? Or any solid suggestions on other resources to look at? I've done some iPhone programming, but not really anything with the graphics API's or custom handling of touch gestures, so I'm not sure where to start.

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  • code throws std::bad_alloc, not enough memory or can it be a bug?

    - by Andreas
    I am parsing using a pretty large grammar (1.1 GB, it's data-oriented parsing). The parser I use (bitpar) is said to be optimized for highly ambiguous grammars. I'm getting this error: 1terminate called after throwing an instance of 'std::bad_alloc' what(): St9bad_alloc dotest.sh: line 11: 16686 Aborted bitpar -p -b 1 -s top -u unknownwordsm -w pos.dfsa /tmp/gsyntax.pcfg /tmp/gsyntax.lex arbobanko.test arbobanko.results Is there hope? Does it mean that it has ran out of memory? It uses about 15 GB before it crashes. The machine I'm using has 32 GB of RAM, plus swap as well. It crashes before outputting a single parse tree. The parser is an efficient CYK chart parser using bit vector representations; I presume it is already near the limit of memory efficiency. If it really requires too much memory I could sample from the grammar rules, but this will decrease parse accuracy of course.

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  • Java library for converting Word documents to PDFs or images

    - by mieze
    Hey there What I need to do is convert Microsoft Word .doc files to PDFs or images. This has to occur in Java. I have done a fair bit of investigation already. I've tried Davisor Publishor but it doesn't give me the accuracy that I need - for instance text overlapping in the output document. Adobe has something called LiveCycle. Anyone tried this? It looks quite massive and a bit of overkill (its an "integrated server solution"). Sounds expensive. Saying that, it doesn't have to be free, or cheap. Even if you just know some names, please shout them my way. Many thanks in advance. Doug

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  • How do I know if I'm being truly clever and not just "clever"?

    - by Covar
    If there's one thing I've learned from programming is that there are clever solutions to problems, and then there are "clever" solutions to problems. One is an intelligent solution to a difficult problem that results in improved efficiency and a better way to to do something and the other will wind up on The Daily WTF, and result in headaches and pain for anyone else involved. My question is how do you distinguish between one and the other? How do you figure out if you've over thought the solution? How do you stop yourself from throwing away truly clever solutions, thinking they were "clever"?

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  • jQuery - Slideshow with different sized images and text

    - by NicoJuicy
    I need some sort of slideshow, with text (something like moving boxes would be nice). I have tried several, but i'm always having problems with different sized images (the images can be for eg. 500px x 300px, but the next one can be 500px, 300px), this gives some problems with the pictures ... I hope you understand what i mean. It's very irritating to find a good jquery plugin that can deal with this problem... :( Can anyone find me a good working one or an alternative to jQuery?

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  • Does Wicket hamper SEO or search engines ability to crawl?

    - by Nick
    We're coming from GWT projects and because of problems with SEO not liking GWT for our next project we're going to move clear of GWT (mainly because seo is a high priority for this next project). In choosing a new framework, I'm looking at Wicket and liking what I've seen so far. I've only done a few tutorials, but in looking at the war layout (from these tutorials) it looks like most of the html pages are in the WEB-INF folder. It this going to cause problems for SEO and search engines crawling through the sites files? Ideally, I'd like to use Wicket with some AJAX and deploy to Google App Engine.

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  • How can I test if a point lies within a 3d shape with its surface defined by a point cloud?

    - by Ben
    Hi I have a collection of points which describe the surface of a shape that should be roughly spherical, and I need a method with which to determine if any other given point lies within this shape. I've previously been approximating the shape as an exact sphere, but this has proven too inaccurate and I need a more accurate method. Simplicity and speed is favourable over complete accuracy, a good approximation will suffice. I've come across techniques for converting a point cloud to a 3d mesh, but most things I have found have been very complicated, and I am looking for something as simple as possible. Any ideas? Many thanks, Ben.

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  • For what purpose does java have a float primitive type?

    - by Roman
    I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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  • Devise and cancan gems: has_many association

    - by tiktak
    I use devise and cancan gems and have simple model association: user has_many subscriptions, subscription belongs_to :user. Have following SubscriptionsController: class SubscriptionsController < ApplicationController load_and_authorize_resource :user load_and_authorize_resource :subscription, through: :user before_filter :authenticate_user! def index @subscriptions = @user.subscriptions.paginate(:page => params[:page]).order(:created_at) end #other actions end And Cancan Ability.rb: class Ability include CanCan::Ability def initialize(user) user ||=User.new can [:index, :show], [Edition, Kind] if user.admin? can :manage, :all elsif user.id can [:read, :create, :destroy, :pay], Subscription, user_id: user.id can [:delete_from_cart, :add_to_cart, :cart], User, id: user.id end end end The problem is that i cannot use subscriptions actions as a user but can as a admin. And have no problems with UsersController. When i delete following lines from SubscriptionsController: load_and_authorize_resource :user load_and_authorize_resource :subscription, through: :user before_filter :authenticate_user! Have no problems at all. So the issue in these lines or in Ability.rb. Any suggestions?

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  • Cuda program results are always zero in HW, correct in EMU??

    - by Orion Nebula
    Hi all! I am having a weird problem .. I have written a CUDA code which executes correctly in emulation and all results show up.. however, when executed on hardware "G210" .. the results in the result memory are always 0 I am passing two vectors to the kernel, one with random variables the other is initialized to zero, the code copies the first vector to shared memory, does some swapping and other operations and then writes back the results on the second vector (the one with the initial 0's) I am using double precision, the -arch sm13 flag is used, all memory allocation also use sizeof(double) .. I have checked if the kernel is invoked, it does .. so no problems here .. the cudaMemCpy has no problems .. what could be the problem .. :( why would it work in emulation but not on HW I am quite confused .. any ideas?

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  • File Encrypt/Decrypt under load?

    - by chopps
    I found an interesting article about encrypting and decrypting files but since it uses a file.dat to store the key this will run into problems when theres alot of users on the site dealing with alot of files. http://www.codeproject.com/KB/security/VernamEncryption.aspx?display=Print Should a new file be created every time a file needs decrypting or would there be a better way to do this? UPDATE: Here is what im using to avoid the locking problems. using (Mutex FileLock = new Mutex(true, System.Guid.NewGuid().ToString())) { try { FileLock.WaitOne(); using (FileStream fs = new FileStream(keyFile, FileMode.Open)) { keyBytes = new byte[fs.Length]; fs.Read(keyBytes, 0, keyBytes.Length); } } catch (Exception ex) { EventLog.LogEvent(ex); } finally { FileLock.ReleaseMutex(); } } I tested it on 1000 TIFFs doing both encryption and decryption without any errors.

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  • What are some useful SQL statements that should be known by all developers who may touch the Back en

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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  • Should class IOException in Java have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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  • manage.py runserver not working

    - by Dan Appleyard
    I am new to django and python in general, so pardon me for any simple mistakes I may be doing. I am trying to setup my first django project on my local windows vista machine. I have created the project successfully with no problems. The issue I am coming across is when my settings.py has values for my database keys, the manage.py runserver command is failing. If I have values in settings before I run the command, as soon as I run it I get errors. If I have already run the command and the server is running, as soon as I edit the settings file with values, the errors show up in my still open command prompt. The inner most exception seems to "Error loading MySQLdb module: No module named MYSQLdb". If I leave the settings.py blank, the command executes with no problems. Any advice would be greatly appreciated! Thanks

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  • Help debugging Apache, Passenger and Rails problem

    - by Matt Dressel
    We have an environment running that uses Apache, Passenger and rails. The system is handling most request normally, yet certain requests do not make it to the rails application. For instance, a request to /books is successful, but /books/1 hits apache and passenger, but does not even make it to rails. We set the apache log level to debug and the passenger log level to 3 so that we could monitor all incoming requests. We could see each request coming through and even the /books/1 request is being handled by passenger. But it never gets to rails. Is there any way to determine where the request goes between Passenger and rails or where debugging information might live? Has anyone ever seen any problems with passenger spawning or queuing? We have spawning set to conservative. Also, we have had some permission/ownership problems in the past, so I am not ruling this out yet. Thanks in advance

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  • Programming language for fast calculations with big integers

    - by sub
    I'm doing Project Euler problems at the moment and I can solve most of them using my own programming language which uses direct C++ integers (so they are bound to 2^32 on my machine). However, at times there are problems which require me to work with very high numbers, I can't do that with native integers. So I implemented a BigInt library in my language which unfortunately gets extremely slow at times. Is there a programming language suitable for very efficient handling of big numbers? I mean that I want to do the things I could do in other programming languages with it (variables, loops, etc.), but in a faster way. If you have got tips for workarounds of the 2^32 limit in my language/C++/other languages, please tell me too!

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