Comments for Noldorin's Blog http://blog.noldorin.com Musings on science, technology, philosophy, and the countless wonders of life Sat, 04 Feb 2012 17:59:50 +0000 hourly 1 http://wordpress.org/?v=3.3.1 Comment on KD-Trees for .NET by Noldorin http://blog.noldorin.com/2011/03/kd-trees-for-dotnet/comment-page-1/#comment-29202 Noldorin Sat, 04 Feb 2012 17:59:50 +0000 http://blog.noldorin.com/?p=952#comment-29202 Hi Cesar. Sorry for the delayed response. If you're still interested; yes, you are right that the check to see whether a node is within the hypersphere should only be made if the list is already "full". I threw together this method quite quickly, and since I don't believe I ever used it in my project, it was never thoroughly tested. (It passed the basic unit tests.) Thanks for pointing it out though. I exclude nodes at the identical location to the search location for semantic reasons. In the application of my project, the input location was that of a star (arbitrary node), and we never wanted to return it back. i.e. It's not technically one of the "nearest neighbours" of a star, but rather the star itself. This should be a trivial change, however, if your application demands it. Glad the implementation was of help. Also, I'd certainly appreciate a patch/fix for the first issue (FindNearestNNeighbors) if you have one. Hi Cesar. Sorry for the delayed response. If you’re still interested; yes, you are right that the check to see whether a node is within the hypersphere should only be made if the list is already “full”. I threw together this method quite quickly, and since I don’t believe I ever used it in my project, it was never thoroughly tested. (It passed the basic unit tests.) Thanks for pointing it out though.

I exclude nodes at the identical location to the search location for semantic reasons. In the application of my project, the input location was that of a star (arbitrary node), and we never wanted to return it back. i.e. It’s not technically one of the “nearest neighbours” of a star, but rather the star itself. This should be a trivial change, however, if your application demands it.

Glad the implementation was of help. Also, I’d certainly appreciate a patch/fix for the first issue (FindNearestNNeighbors) if you have one.

]]> Comment on KD-Trees for .NET by César http://blog.noldorin.com/2011/03/kd-trees-for-dotnet/comment-page-1/#comment-29186 César Sun, 08 Jan 2012 23:59:40 +0000 http://blog.noldorin.com/?p=952#comment-29186 Hey Noldorin, looking at FindNearestNNeighbors I see that you only insert values into the list when they are within the hypersphere of smaller distance. However, this only makes sense when the size of the list is numNeighbors; before that, you should probably add to the list every value you come across. Otherwise, you might have the closest value your location at the root, which would result in a small hypersphere and no more elements would be picked. Am I missing something? Also, why would you remove from the output a node just because it is the search location? As any other value in the tree, I would expect it goes into the output. Is there any restriction I'm not aware of? In any case, thanks for the code. It's very useful! Hey Noldorin, looking at FindNearestNNeighbors I see that you only insert values into the list when they are within the hypersphere of smaller distance. However, this only makes sense when the size of the list is numNeighbors; before that, you should probably add to the list every value you come across. Otherwise, you might have the closest value your location at the root, which would result in a small hypersphere and no more elements would be picked. Am I missing something?

Also, why would you remove from the output a node just because it is the search location? As any other value in the tree, I would expect it goes into the output. Is there any restriction I’m not aware of?

In any case, thanks for the code. It’s very useful!

]]> Comment on The Hardest Logic Puzzle Ever by Noldorin http://blog.noldorin.com/2011/12/the-hardest-logic-puzzle-ever/comment-page-1/#comment-29182 Noldorin Sat, 07 Jan 2012 16:04:27 +0000 http://blog.noldorin.com/?p=1033#comment-29182 For those who are so inclined, there has been some vaguely interesting discussion/comments on this post over at the Math sub-Reddit. http://www.reddit.com/r/math/comments/nwtcz/the_hardest_logic_puzzle_ever_an_excursion_into_a/ For those who are so inclined, there has been some vaguely interesting discussion/comments on this post over at the Math sub-Reddit.

http://www.reddit.com/r/math/comments/nwtcz/the_hardest_logic_puzzle_ever_an_excursion_into_a/

]]> Comment on The Traveller’s Paradox by The Hardest Logic Puzzle Ever « Noldorin's Blog http://blog.noldorin.com/2010/03/the-travellers-paradox/comment-page-1/#comment-28216 The Hardest Logic Puzzle Ever « Noldorin's Blog Fri, 30 Dec 2011 02:07:27 +0000 http://blog.noldorin.com/?p=543#comment-28216 [...] time ago I wrote a post about the well-known logic puzzle of The Traveller’s Paradox and attempted to derive and justify a solution using the formal methods of propositional calculus [...] [...] time ago I wrote a post about the well-known logic puzzle of The Traveller’s Paradox and attempted to derive and justify a solution using the formal methods of propositional calculus [...]

]]> Comment on KD-Trees for .NET by Noldorin http://blog.noldorin.com/2011/03/kd-trees-for-dotnet/comment-page-1/#comment-23702 Noldorin Thu, 17 Nov 2011 02:07:04 +0000 http://blog.noldorin.com/?p=952#comment-23702 Hi Ian. You're absolutely right. I added the CS file for the unit tests at a later date, having updated the core KdTree implementation in the meanwhile (for my FermiSim project, linked above). I've now updated the KdTree.cs and KdTreeNode.cs files to reflect the latest revision of my project (now inactive). It provides the requisite n-nearest-neighbours implementation. Hope that helps. Hi Ian.

You’re absolutely right. I added the CS file for the unit tests at a later date, having updated the core KdTree implementation in the meanwhile (for my FermiSim project, linked above). I’ve now updated the KdTree.cs and KdTreeNode.cs files to reflect the latest revision of my project (now inactive). It provides the requisite n-nearest-neighbours implementation.

Hope that helps.

]]> Comment on KD-Trees for .NET by Ian http://blog.noldorin.com/2011/03/kd-trees-for-dotnet/comment-page-1/#comment-23595 Ian Wed, 16 Nov 2011 02:26:27 +0000 http://blog.noldorin.com/?p=952#comment-23595 Hi Noldorin, thank you very much for your work on this. I'm attempting to leverage you code and ran into a problem compiling the KdTreeTests.cs. In the Find TestFindNearestNNeighbours method it looks like the test is calling a method that doesn't appear to be implimented in the KdTree class that would allow you to find the nearest N Neighbours instead of only nearest Neighbour. Is there a version of your work that includes an overloaded FindNearestNeighbours method that will search for multiple Neighbours? Hi Noldorin, thank you very much for your work on this. I’m attempting to leverage you code and ran into a problem compiling the KdTreeTests.cs. In the Find TestFindNearestNNeighbours method it looks like the test is calling a method that doesn’t appear to be implimented in the KdTree class that would allow you to find the nearest N Neighbours instead of only nearest Neighbour. Is there a version of your work that includes an overloaded FindNearestNeighbours method that will search for multiple Neighbours?

]]> Comment on Numerical Analysis for .NET by Noldorin http://blog.noldorin.com/2009/05/numerical-analysis-for-net/comment-page-1/#comment-23325 Noldorin Sun, 13 Nov 2011 04:12:02 +0000 http://alexreg.wordpress.com/?p=185#comment-23325 A quick update (I'm sorry for the lack of progress on this front): I've checked into adding this functionality, and have had more feedback from the Math.NET Numerics team. Basically, it makes sense to wait until they have rewritten their sparse linear algebra code, which is being released very soon. I'll be getting right on adding ARPACK features to the library after that! A quick update (I’m sorry for the lack of progress on this front): I’ve checked into adding this functionality, and have had more feedback from the Math.NET Numerics team. Basically, it makes sense to wait until they have rewritten their sparse linear algebra code, which is being released very soon. I’ll be getting right on adding ARPACK features to the library after that!

]]> Comment on Starting Tutoring by teusje http://blog.noldorin.com/2011/10/starting-tutoring/comment-page-1/#comment-23224 teusje Fri, 11 Nov 2011 21:39:21 +0000 http://blog.noldorin.com/?p=1011#comment-23224 I hope you will enjoy your choice! Good luck mate! :-) I hope you will enjoy your choice!
Good luck mate! :-)

]]> Comment on KD-Trees for .NET by Qua http://blog.noldorin.com/2011/03/kd-trees-for-dotnet/comment-page-1/#comment-22372 Qua Mon, 31 Oct 2011 18:22:37 +0000 http://blog.noldorin.com/?p=952#comment-22372 Try adding the nodes (0,0) followed by (0,1) and then remove (0,1) and see if the tree is what you expected. Try adding the nodes (0,0) followed by (0,1) and then remove (0,1) and see if the tree is what you expected.

]]> Comment on Writing a Parser in C# by Christopher Diggins http://blog.noldorin.com/2009/09/writing-a-parser-in-csharp/comment-page-1/#comment-22362 Christopher Diggins Mon, 31 Oct 2011 13:35:10 +0000 http://noldorin.com/blog/?p=291#comment-22362 I've written my own article on writing parsers in C# using C# 4.0 which I posted on CodeProject.com. It contains more in-depth examples and less theory than the article you reference but you might find it interesting nonetheless. http://www.codeproject.com/KB/recipes/programminglanguagetoools.aspx I’ve written my own article on writing parsers in C# using C# 4.0 which I posted on CodeProject.com. It contains more in-depth examples and less theory than the article you reference but you might find it interesting nonetheless. http://www.codeproject.com/KB/recipes/programminglanguagetoools.aspx

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