Function auto_threads 

pub fn auto_threads() -> usize

Worker threads of a search whose caller fixed none: this machine’s CPUs split between this process and the user’s other busy registered ones (auto_threads_for). Re-read at most every 100 ms, so a sweep follows the others starting and finishing their scans (Threads::wait_turn). A process that does not register itself (a one-shot command) still gives way to the resident hosts.