datatable.options.nthreads

The number of threads used by datatable internally.

Many calculations in datatable module are parallelized. This setting controls how many threads will be used during such calculations.

Initially, this option is set to the value returned by C++ call std::thread::hardware_concurrency(). This is usually equal to the number of available cores.

You can set nthreads to a value greater or smaller than the initial setting. For example, setting nthreads = 1 will force the library into a single-threaded mode. Setting nthreads to 0 will restore the initial value equal to the number of processor cores. Setting nthreads to a value less than 0 is equivalent to requesting that fewer threads than the maximum.