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Mikhail Konnik

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Company/University
The University of Newcastle, Australia

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Professional Interests:
adaptive optics, images processing

 

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Comments and Ratings by Mikhail View all
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21 Sep 2014 updownsample up/down sample an input matrix using the fourier domain. Author: Ohad Gal

@ David Felguera

Well, technically speaking the code is correct - in terms of what _exactly_ is it doing. The code claims to do downSAMPLING, which is just throwing away specified frequencies. Unlike the _decimation_, which uses the low-pass filtering to mitigate the downsampling effects (slower and more complicated).

The effect that you experiencing in this example is called ringing, and this exactly what happens in up/downsampling without filtering.

21 Sep 2014 updownsample up/down sample an input matrix using the fourier domain. Author: Ohad Gal

21 Aug 2014 Fast Symmetric Positive Definite Matrix Inverse Uses LAPACK, Cholesky to invert real, positive definite, symmetric matrix. Faster than inv. Author: Eric Blake

Thanks for the updated code, Eric!
Works like a charm.

On a side note, and I think it is worth mentioning in the description that the speed-up is noticeable when the matrices are large (in the current example they are small). In my case, I have to solve a big least-squares problem - and invChol, literally, saves the day.

29 Jul 2014 Fast Symmetric Positive Definite Matrix Inverse Uses LAPACK, Cholesky to invert real, positive definite, symmetric matrix. Faster than inv. Author: Eric Blake

Excellent code, simple yet efficient, thank you!

One comment. When I compile this in Linux (x86) on MATLAB 2009, I'm getting these warnings:

/opt/matlab/bin/mex invChol_mex.c -lmwlapack

invChol_mex.c: In function ‘mexFunction’:
invChol_mex.c:75: warning: implicit declaration of function ‘dpotrf_’
invChol_mex.c:87: warning: implicit declaration of function ‘dpotri_’
invChol_mex.c:111: warning: implicit declaration of function ‘spotrf_’
invChol_mex.c:123: warning: implicit declaration of function ‘spotri_’

Not critical, of course, but still.

03 Sep 2012 fwhm To calculate the full-width at half-maximum of an input. Author: Patrick Egan

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