Wrapper of a single dart_unit_locality_t object. More...

#include <UnitLocality.h>

Public Member Functions
	UnitLocality (const dash::Team &team, team_unit_t unit)

	UnitLocality (global_unit_t unit)

	UnitLocality (const UnitLocality &)=default

UnitLocality &	operator= (const UnitLocality &)=default

const dart_hwinfo_t &	hwinfo () const

dart_hwinfo_t &	hwinfo ()

dart_domain_locality_t &	domain ()

const dart_domain_locality_t &	domain () const

const dash::Team &	team () const

team_unit_t	unit_id () const

dash::util::LocalityDomain &	node_domain ()

dash::util::LocalityDomain	parent ()

dash::util::LocalityDomain	parent_in_scope (dash::util::Locality::Scope scope)

std::string	domain_tag () const

std::string	host () const

void	set_domain_tag (const std::string &tag)

void	set_host (const std::string &hostname)

int	num_cores () const

int	min_threads ()

int	max_threads ()

int	num_threads () const

int	num_numa () const

int	numa_id () const

int	cpu_id () const

int	cpu_mhz () const

int	max_shmem_mbps () const

int	max_cpu_mhz ()

int	min_cpu_mhz ()

int	cache_line_size (int cache_level)

std::string	hostname ()

int	num_domain_threads ()
	Number of threads currently available to the active unit. More...

Detailed Description

Wrapper of a single dart_unit_locality_t object.

Definition at line 30 of file UnitLocality.h.

Member Function Documentation

◆ num_domain_threads()

int dash::util::UnitLocality::num_domain_threads ( )

inline

Number of threads currently available to the active unit.

The returned value is calculated from unit locality data and hardware specifications and can, for example, be used to set the num_threads parameter of OpenMP sections:

#ifdef DASH_ENABLE_OPENMP
  auto n_threads = dash::util::Locality::NumUnitDomainThreads();
  if (n_threads > 1) {
    #pragma omp parallel num_threads(n_threads) private(t_id)
    {
       // ...
    }
#endif

The following configuration keys affect the number of available threads:

DASH_DISABLE_THREADS: If set, disables multi-threading at unit scope and this method returns 1.
DASH_MAX_SMT: If set, virtual SMT CPUs (hyperthreads) instead of physical cores are used to determine availble threads.
DASH_MAX_UNIT_THREADS: Specifies the maximum number of threads available to a single unit.

Note that these settings may differ between hosts.

Example for MPI:

mpirun -host node.0 -env DASH_MAX_UNIT_THREADS 4 -n 16 myprogram : -host node.1 -env DASH_MAX_UNIT_THREADS 2 -n 32 myprogram

The DASH configuration can also be changed at run time with the dash::util::Config interface.

See also: dash::util::Config; dash::util::TeamLocality

Definition at line 306 of file UnitLocality.h.

Referenced by dash::fill(), and dash::min_element().

   {
     auto n_threads = num_cores();
     if (dash::util::Config::get<bool>("DASH_DISABLE_THREADS")) {
       // Threads disabled in unit scope:
       n_threads  = 1;
     } else if (dash::util::Config::get<bool>("DASH_MAX_SMT")) {
       // Configured to use SMT (hyperthreads):
       n_threads *= max_threads();
     } else {
       // Start one thread on every physical core assigned to this unit:
       n_threads *= min_threads();
     }
     if (dash::util::Config::is_set("DASH_MAX_UNIT_THREADS")) {
       n_threads  = std::min(dash::util::Config::get<int>(
                               "DASH_MAX_UNIT_THREADS"),
                             n_threads);
     }
     return n_threads;
   }

The documentation for this class was generated from the following file:

/tmp/tmporruphar/dash/include/dash/util/UnitLocality.h

Public Member Functions

Detailed Description

Member Function Documentation

◆ num_domain_threads()