Writing Fast MATLAB Code

Good, Thanks!

Good work!

Great, Thanks!

Good, Thanks!

Thanks sometimes pdf are better than m-file.

Thanks a lot for this. A much for any people speaks MATLAB.

Indeed, a very good read ... should talk about things like bsxfun and how mex files compare to past and current matlab speeds. How about a section on I/O and string parsing.

good

Kudos, very informative and well written. Thank you for your good efforts!

wow its very exciting

very usefull

thx

Very useful tip!! I love it

I love it, Azalin.. way to face off against bad grammar with even worse...

Very good short introduction to optimizing m-files!

fair try

Very good

Thanks you are really good people

Great Job

A very good outline of advanced Matlab tips. Well worth reading.

Yes it's a good idea to use the profiler. Using the profiler, I found that Pascal's recommended matrix initial code A = s(ones(m,n)) is four times slower than the simpler A(1:m,1:n) = s or A = s +zeros(m,n)

fillfull

Helpful.

As a beginner, I have found everything clear, fast reading, and useful. Good job!

Very good description of the indexing features of matlab. Please not that transposing a matrix using ' will complex conjungate the elements aswell. Therefore to create a row-vector by A(:)' should be done with care. Alternatively I think that transpose(A(:)) should be used.

Thanks, this is a great basic guide to speeding up Matlab code. I wish I had it a year ago when I started with Matlab.

As a note though, the method shown to avoid repmat is rarely faster (in Matlab 6.5) and usually slower than actually using repmat.

But thanks for the work you put into this, I printed it out and keep it next to Richard Johnson's "Matlab Programming Style Guidelines" on my ML shelf.

***Response to review***

I'm sorry this article wasn't helpful, perhaps it is too introductory for you. Responding to your points:

(1) ?numel? is not a function as of MATLAB 5.3 (what usually work with). It is a standard function by version 6.1.

(2) It is true that min and max operate over columns rather than entire matrices (the article includes some discussion on this). Thus the suggested methods involving min and max include matrix to vector conversion (using "A(:)" changes A to a vector). It works for matrices and n-D matrices of all sizes.

(3) The advantage of the not repmat method is that there is no function call -- it won't be significantly faster for a single tiling but can make a difference for many separate tiling operations. Furthermore, the standard m-files in MATLAB 4.0 and earlier don't include repmat, so this method is also more compatible.

(4) MEX is not a topic of discussion in this article, only mentioned. I agree it is much more difficult to write and peer and should only be a last resort.

(5) And yes, looping has a fair bit of overhead. Try the profiler on a for loop with many iterations and a one-line inner loop.