This option controls the number of threads used by datatable for parallel calculations.

## Parameters¶

return
int

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

int
New nthreads value. It can be 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.