How to set the max number of workers in parpool/matlabpool from console?

Question

I know how to change the maximum number of workers using the Parallel preferences window in Matlab, but I cannot find any documentation about how to make changes on the preferences from console/code, and specifically about how to change the maximum number of workers I can use in a forloop. Any help will be greatly appreciated.

Answer 1

You want the parpool function. With no arguments it creates a default number of workers, with an integer argument it creates that many workers. If you just use a parfor loop without calling it, you get the default number for your profile, but I'm not sure where that is set. There's more documentation on the mathworks website: http://www.mathworks.com/help/distcomp/parpool.html

The maximum number of workers should be effectively as large as you want, but you will stop gaining any efficiency if you create more workers than you have processors. Let me know if you need any advice on picking a good number of workers.