Hi Farouk,
By default Parallel Computing Toolbox will attempt to use a number of workers equal to the number physical cores of the computer. In a cloud environment, a vCPU typically represents a portion of a physical CPU core.
To programmatically alter the maximum number of workers allowed by the 'Processes' or 'local' profile, use:
c = parcluster('Processes')
c.NumWorkers = 8;
saveProfile(c) % will overwrite the profile with the new NumWorkers value
Please also refer to http://www.mathworks.com/matlabcentral/answers/2042101-how-can-i-increase-the-number-of-matlab-workers-inside-parallel-computing-toolbox-to-use-all-the-log for information on why the number of cores detected might not be all of the cores on your machine.
Hope this helps.
