When I try your example on Linux (Debian 9) using GCC I see a good speedup with
parfor
in generated MEX:
for: time = 1.3s
parfor: time = 0.4s
On Windows 10 using Microsoft Visual Studio 2017, I see a much more modest speedup:
for: time = 1.3s
parfor: time = 1.0s
What compiler and OS are you using?
One thing that may be happening for certain compilers is that each of the
parfor
loop iterations are very fast. When this is the case, the overhead of managing threads can dominate the loop execution time. This can ruin any possible parallelism gains.
The Coder documentation covers this in some detail:
as does the MATLAB
parfor
documentation:
