## Which MATLAB functions are multicore aware?

In order to write fully parallel programs in MATLAB you have a few choices but they are either hard work, expensive or both. For example you could

- Write parallel mex files using C and OpenMP
- Drop a load of cash on the parallel computing toolbox from the Mathworks
- Use the free parallel toolbox, pMATLAB

Wouldn’t it be nice if you could do no work at all and yet STILL get a speedup on a multicore machine? Well, you can….sometimes.

Slowly but surely, The Mathworks are parallelising some of the built in MATLAB functions to make use of modern multicore processors. So, for certain functions you will see a speed increase in your code when you move to a dual or quad core machine. But which functions?

On a recent train journey I trawled through all of the release notes in MATLAB and did my best to come up with a definitive list and the result is below.

Alongside each function is the version of MATLAB where it first became parallelised (if known). If there is any extra detail then I have included it in brackets (typically things like – ‘this function is only run in parallel for input arrays of more than 20,000 elements’). I am almost certainly missing some functions and details so if you know something that I don’t then please drop me a comment and I’ll add it to the list.

Of course when I came to write all of this up I did some googling and discovered that The Mathworks have already answered this question themselves! Oh well….I’ll publish my list anyway.

**Update 11th May 2012** While optimising a user’s application, I discovered that the pinv function makes use of multicore processors so I’ve added it to the list. pinv makes use of svd which is probably the bit that’s multithreaded.

**Update 18th February 2012:** Added a few functions that I had missed earlier: erfcinv, rank,isfinite,lu and schur. Not sure when they became multithreaded so left the version number blank for now

**Update 16th June 2011: **Added new functions that became multicore aware in version 2011a plus a couple that have been multicore for a while but I just didn’t know about them!

**Update 8th March 2010:** Added new functions that became multicore aware in version 2010a. Also added multicore aware functions from the image processing toolbox.

abs (for double arrays > 200k elements),2007a acos (for double arrays > 20k elements),2007a acosh (for double arrays > 20k elements),2007a applylut,2009b (Image processing toolbox) asin (for double arrays > 20k elements),2007a asinh(for double arrays > 20k elements),2007a atan (for double arrays > 20k elements),2007a atand (for double arrays > 20k elements),2007a atanh (for double arrays > 20k elements),2007a backslash operator (A\b for double arrays > 40k elements),2007a bsxfun,2009b bwmorph,2010a (Image processing toolbox) bwpack,2009b (Image processing toolbox) bwunpack,2009b (Image processing toolbox) ceil (for double arrays > 200k elements),2007a conv,2011a conv2,(two input form),2010a cos (for double arrays > 20k elements),2007a cosh (for double arrays > 20k elements),2007a det (for double arrays > 40k elements),2007a edge,2010a (Image processing toolbox) eig erf,2009b erfc,2009b erfcinv erfcx,2009b erfinv,2009b exp (for double arrays > 20k elements),2007a expm (for double arrays > 40k elements),2007a fft,2009a fft2,2009a fftn,2009a filter,2009b fix (for double arrays > 200k elements),2007a floor (for double arrays > 200k elements),2007a gamma,2009b gammaln,2009b hess (for double arrays > 40k elements),2007a hypot (for double arrays > 200k elements),2007a ifft,2009a ifft2,2009a ifftn,2009a imabsdiff,2010a (Image processing toolbox) imadd,2010a (Image processing toolbox) imclose,2010a (Image processing toolbox) imdilate,2009b (Image processing toolbox) imdivide,2010a (Image processing toolbox) imerode,2009b (Image processing toolbox) immultiply,2010a (Image processing toolbox) imopen,2010a (Image processing toolbox) imreconstruct,2009b (Image processing toolbox) int16 (for double arrays > 200k elements),2007a int32 (for double arrays > 200k elements),2007a int8 (for double arrays > 200k elements),2007a inv (for double arrays > 40k elements),2007a iradon,2010a (Image processing toolbox) isfinite isinf (for double arrays > 200k elements),2007a isnan (for double arrays > 200k elements),2007a ldivide,2008a linsolve (for double arrays > 40k elements),2007a log,2008a log2,2008a logical (for double arrays > 200k elements),2007a lscov (for double arrays > 40k elements),2007a lu Matrix Multiply (X*Y - for double arrays > 40k elements),2007a Matrix Power (X^N - for double arrays > 40k elements),2007a max (for double arrays > 40k elements),2009a medfilt2,2010a (Image processing toolbox) min (for double arrays > 40k elements),2009a mldivide (for sparse matrix input),2009b mod (for double arrays > 200k elements),2007a pinv pow2 (for double arrays > 20k elements),2007a prod (for double arrays > 40k elements),2009a qr (for sparse matrix input),2009b qz,2011a rank rcond (for double arrays > 40k elements),2007a rdivide,2008a rem,2008a round (for double arrays > 200k elements),2007a schur sin (for double arrays > 20k elements),2007a sinh (for double arrays > 20k elements),2007a sort (for long matrices),2009b sqrt (for double arrays > 20k elements),2007a sum (for double arrays > 40k elements),2009a svd, tan (for double arrays > 20k elements),2007a tand (for double arrays > 200k elements),2007a tanh (for double arrays > 20k elements),2007a unwrap (for double arrays > 200k elements),2007a various operators such as x.^y (for double arrays > 20k elements),2007a Integer conversion and arithmetic,2010a

Hello,

Any updates on functions from 2010b and the upcoming 2011a release?

Hi Lee

I’ve not combed through 2010b looking for additions yet.

Won’t be able to talk about 2011a until the release.

Cheers,

Mike

The functions I know about in 2011a have been added