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15 Mar 2011 (Updated )

Do: C = frontal_mtimes(A, b); not: for k=1:size(A,3), C(:,:,k) = A(:,:,k) * b(:,:,k); end

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These routines assist in the manipulation of matrices with same shape but different content. For example, performing the product A*b is trivial for matrix A and vector b, but what would you do if you had several such products to form? Examples abound: rotations, Jacobians, covariances, etc. Using the frontal routines, you'd collect them all in a three-dimensional matrix or third-order tensor, with each k-th frontal panel of A(:,:,k) and b(:,:,k) storing one such a related matrix and vector. Then calling

  C = frontal_mtimes(A, b);

would do the equivalent of

  for k=1:size(A,3), C(:,:,k) = A(:,:,k) * b(:,:,k); end

but using internally different algorithms depending on the dimensions of A (including a C-mex option). If you like operator overloading, you can do instead:

  A = frontal(A);
  b = frontal(b);
  C = A*b;

You might want to compile the file frontal_mtimes_helper.c, but it's not required.

After you've unzipped it, test your installation running:


(don't do addpath(genpath('c:\work\fx\frontal\frontal\')))


Testit, Multiple Matrix Multiplications, With Array Expansion Enabled, and Mtimesx Fast Matrix Multiply With Multi Dimensional Support inspired this file.

MATLAB release MATLAB 7.9 (R2009b)
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Comments and Ratings (4)
16 Mar 2011 Felipe G. Nievinski

Don't do:




as instructed.

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16 Mar 2011 James Tursa

James Tursa (view profile)

OK. I think I have it working now, at least partially. I had to add both the frontal directory *and* the util subdirectory to the path.

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16 Mar 2011 Felipe G. Nievinski

Please check your unzipping procedure. I've double checked the zip and the directory structure is intact.

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16 Mar 2011 James Tursa

James Tursa (view profile)

FYI: From the "Other Files" display above it looks like the intent is to install this as a class directory structure with some helper files. But when the zip file is downloaded there is no such directory structure. All I get is a bunch of files. So I will have to manually build the @frontal folder and then separate out the helper functions also, maybe putting them in a private directory under @frontal. Is it your intent that a person who downloads this has to build all these directory structures manually?

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16 Mar 2011 1.1

clarified paths

16 Apr 2011 1.2

added acknowledgements; applied more tags.

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