Parfor without having a matlabpool open in slower than the comparative for loop so I guess it should be doing something different.
tic parfor i=1:10000*1024
Output: Elapsed time is 25.464860 seconds.
Same code without the parfor
tic for i=1:10000*1024
Output: Elapsed time is 1.121148 seconds.
However with the matlabpool open the same parfor loop was much faster matlabpool open local 8
Elapsed time is 4.462031 seconds.
(FYI I have a dual processor quad core machine with 16GB of ram)