std::experimental::parallel::seq,std::experimental::parallel::par, (3) Linux Manual Page

std::experimental::parallel::seq,std::experimental::parallel::par, – std::experimental::parallel::seq,std::experimental::parallel::par,

Synopsis

Defined in header <experimental/execution_policy>
constexpr sequential_execution_policy seq{};           (parallelism TS)
constexpr parallel_execution_policy par{};             (parallelism TS)
constexpr parallel_vector_execution_policy par_vec{};  (parallelism TS)
seq, par and par_vec are instances of the execution policy types
sequential_execution_policy, parallel_execution_policy and
parallel_vector_execution_policy respectively. They are used to specify the
execution policy of parallel algorithms – i.e., the kinds of parallelism allowed.