Comments on: Evens and Odds http://blogs.mathworks.com/loren/2009/08/13/evens-and-odds/ Loren Shure works on design of the MATLAB language at MathWorks. She writes here about once a week on MATLAB programming and related topics. Thu, 09 Feb 2012 04:19:21 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Joachim http://blogs.mathworks.com/loren/2009/08/13/evens-and-odds/#comment-30538 Joachim Tue, 18 Aug 2009 03:34:14 +0000 http://blogs.mathworks.com/loren/2009/08/13/evens-and-odds/#comment-30538 Very interesting post, Loren. Unfortunately, I don't have an example application. Just wanted to point out that it appears a bitwise logical AND comparison would be more efficient than a modulus operation. To compute the modulus, you have to do a division which tends to be costly computationally... So I find Urs' code appealing from that perspective. Not 100% sure about Matlab though. What I have in mind is that, AFAIK, C compilers optimize (x%2) to (x&1) if the two are equivalent on the architecture. Very interesting post, Loren. Unfortunately, I don’t have an example application.

Just wanted to point out that it appears a bitwise logical AND comparison would be more efficient than a modulus operation. To compute the modulus, you have to do a division which tends to be costly computationally… So I find Urs’ code appealing from that perspective. Not 100% sure about Matlab though. What I have in mind is that, AFAIK, C compilers optimize (x%2) to (x&1) if the two are equivalent on the architecture.

]]> By: Emilie S. http://blogs.mathworks.com/loren/2009/08/13/evens-and-odds/#comment-30530 Emilie S. Fri, 14 Aug 2009 11:19:51 +0000 http://blogs.mathworks.com/loren/2009/08/13/evens-and-odds/#comment-30530 This is very impressive indeed. Urs Schwarz's contribution appears very genius and I will be looking in to this isodd. This is very impressive indeed. Urs Schwarz’s contribution appears very genius and I will be looking in to this isodd.

]]> By: Ben http://blogs.mathworks.com/loren/2009/08/13/evens-and-odds/#comment-30528 Ben Fri, 14 Aug 2009 01:06:05 +0000 http://blogs.mathworks.com/loren/2009/08/13/evens-and-odds/#comment-30528 One function that I often have to be careful with, is using HIST to count unique members of an array: <pre> [n,u]=hist(x,unique(x)); </pre> This works fine unless x has only one unique element. There is a good submission on FEX that solves this problem but it would be nice to see a built-in version. Also, anyone working with large integers (bigger than bitmax) should look at John D'Errico's marvellous Variable Precision Integer toolbox. One function that I often have to be careful with, is using HIST to count unique members of an array:

[n,u]=hist(x,unique(x));

This works fine unless x has only one unique element. There is a good submission on FEX that solves this problem but it would be nice to see a built-in version.

Also, anyone working with large integers (bigger than bitmax) should look at John D’Errico’s marvellous Variable Precision Integer toolbox.

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