fminbnd in parallel: no gain

I want to minimize a function using fminbnd on a 32-core Linux machine (running Ubuntu 13.10+matlab2013a). I do the following:

>>matlabpool

Starting matlabpool using the 'local' profile ...
connected to 12 workers

>>optim_fminbnd=optimset('fminbnd');

>>tic

>>disp('With parallelization:')

With parallelization:

>> fminbnd(@localstrul_valuespectral,0,359,optimset(optim_fminbnd,'UseParallel','a
lways'))

ans =

    221.8743

>>toc

Elapsed time is 7.124580 seconds.

>>tic

>>disp('Without parallelization:')

Without parallelization:

>>fminbnd(@localstrul_valuespectral,0,359,optimset(optim_fminbnd,'UseParallel','ne
ver'))

ans =

    221.8743

>>toc

Elapsed time is 7.785863 seconds

that is to say there is no gain in speed (sometimes the non-parallel version is marginally faster). Do I set the parameters wrong?

Answer 1

[Alan Weiss]

fminbnd is a serial algorithm. There is no gain possible using parallel processing. In fact, look at the options for fminbnd, and you see that fminbnd does not use the UseParallel option.

Alan Weiss

MATLAB mathematical toolbox documentation

[Matt J]

However, it might be possible to use parallel operations inside the objective function localstrul_valuespectral to speed up its evluations.