Work Sharing

Enumerations
enum	sched_type {   kmp_sch_lower = 32, kmp_sch_static_chunked = 33, kmp_sch_static = 34, kmp_sch_dynamic_chunked = 35,   kmp_sch_guided_chunked = 36, kmp_sch_runtime = 37, kmp_sch_auto = 38, kmp_sch_trapezoidal = 39,   kmp_sch_static_greedy = 40, kmp_sch_static_balanced = 41, kmp_sch_guided_iterative_chunked = 42, kmp_sch_guided_analytical_chunked = 43,   kmp_sch_static_steal = 44, kmp_sch_upper = 45, kmp_ord_lower = 64, kmp_ord_static_chunked = 65,   kmp_ord_static = 66, kmp_ord_dynamic_chunked = 67, kmp_ord_guided_chunked = 68, kmp_ord_runtime = 69,   kmp_ord_auto = 70, kmp_ord_trapezoidal = 71, kmp_ord_upper = 72, kmp_nm_lower = 160,   kmp_nm_static_chunked = 161, kmp_nm_static = 162, kmp_nm_dynamic_chunked = 163, kmp_nm_guided_chunked = 164,   kmp_nm_runtime = 165, kmp_nm_auto = 166, kmp_nm_trapezoidal = 167, kmp_nm_static_greedy = 168,   kmp_nm_static_balanced = 169, kmp_nm_guided_iterative_chunked = 170, kmp_nm_guided_analytical_chunked = 171, kmp_nm_static_steal = 172,   kmp_nm_ord_static_chunked = 193, kmp_nm_ord_static = 194, kmp_nm_ord_dynamic_chunked = 195, kmp_nm_ord_guided_chunked = 196,   kmp_nm_ord_runtime = 197, kmp_nm_ord_auto = 198, kmp_nm_ord_trapezoidal = 199, kmp_nm_upper = 200,   kmp_sch_default = kmp_sch_static }
Functions
void	__kmpc_critical (ident_t *loc, kmp_int32 global_tid, kmp_critical_name *crit)
void	__kmpc_end_critical (ident_t *loc, kmp_int32 global_tid, kmp_critical_name *crit)
void	__kmpc_end_master (ident_t *loc, kmp_int32 global_tid)
void	__kmpc_end_ordered (ident_t *loc, kmp_int32 gtid)
void	__kmpc_end_single (ident_t *loc, kmp_int32 global_tid)
void	__kmpc_for_static_fini (ident_t *loc, kmp_int32 global_tid)
kmp_int32	__kmpc_master (ident_t *loc, kmp_int32 global_tid)
void	__kmpc_ordered (ident_t *loc, kmp_int32 gtid)
kmp_int32	__kmpc_single (ident_t *loc, kmp_int32 global_tid)
void	__kmpc_dispatch_init_4 (ident_t *loc, kmp_int32 gtid, enum sched_type schedule, kmp_int32 lb, kmp_int32 ub, kmp_int32 st, kmp_int32 chunk)
void	__kmpc_for_static_init_4 (ident_t *loc, kmp_int32 gtid, kmp_int32 schedtype, kmp_int32 *plastiter, kmp_int32 *plower, kmp_int32 *pupper, kmp_int32 *pstride, kmp_int32 incr, kmp_int32 chunk)
void	__kmpc_for_static_init_4u (ident_t *loc, kmp_int32 gtid, kmp_int32 schedtype, kmp_int32 *plastiter, kmp_uint32 *plower, kmp_uint32 *pupper, kmp_int32 *pstride, kmp_int32 incr, kmp_int32 chunk)
void	__kmpc_for_static_init_8 (ident_t *loc, kmp_int32 gtid, kmp_int32 schedtype, kmp_int32 *plastiter, kmp_int64 *plower, kmp_int64 *pupper, kmp_int64 *pstride, kmp_int64 incr, kmp_int64 chunk)
void	__kmpc_for_static_init_8u (ident_t *loc, kmp_int32 gtid, kmp_int32 schedtype, kmp_int32 *plastiter, kmp_uint64 *plower, kmp_uint64 *pupper, kmp_int64 *pstride, kmp_int64 incr, kmp_int64 chunk)

---

Detailed Description

These functions are used for implementing #pragma omp for, #pragma omp sections, #pragma omp single and #pragma omp master constructs.

When handling loops, there are different functions for each of the signed and unsigned 32 and 64 bit integer types which have the name suffixes `_4`, `_4u`, `_8` and `_8u`. The semantics of each of the functions is the same, so they are only described once.

Static loop scheduling is handled by __kmpc_for_static_init_4 and friends. Only a single call is needed, since the iterations to be executed by any give thread can be determined as soon as the loop parameters are known.

Dynamic scheduling is handled by the __kmpc_dispatch_init_4 and __kmpc_dispatch_next_4 functions. The init function is called once in each thread outside the loop, while the next function is called each time that the previous chunk of work has been exhausted.

---

Enumeration Type Documentation

enum sched_type

Describes the loop schedule to be used for a parallel for loop.

Enumerator:

kmp_sch_lower	lower bound for unordered values
kmp_sch_static_chunked
kmp_sch_static	static unspecialized
kmp_sch_dynamic_chunked
kmp_sch_guided_chunked	guided unspecialized
kmp_sch_runtime
kmp_sch_auto	auto
kmp_sch_trapezoidal
kmp_sch_static_greedy
kmp_sch_static_balanced
kmp_sch_guided_iterative_chunked
kmp_sch_guided_analytical_chunked
kmp_sch_static_steal	accessible only through KMP_SCHEDULE environment variable
kmp_sch_upper	upper bound for unordered values
kmp_ord_lower	lower bound for ordered values, must be power of 2
kmp_ord_static_chunked
kmp_ord_static	ordered static unspecialized
kmp_ord_dynamic_chunked
kmp_ord_guided_chunked
kmp_ord_runtime
kmp_ord_auto	ordered auto
kmp_ord_trapezoidal
kmp_ord_upper	upper bound for ordered values
kmp_nm_lower	lower bound for nomerge values
kmp_nm_static_chunked
kmp_nm_static	static unspecialized
kmp_nm_dynamic_chunked
kmp_nm_guided_chunked	guided unspecialized
kmp_nm_runtime
kmp_nm_auto	auto
kmp_nm_trapezoidal
kmp_nm_static_greedy
kmp_nm_static_balanced
kmp_nm_guided_iterative_chunked
kmp_nm_guided_analytical_chunked
kmp_nm_static_steal
kmp_nm_ord_static_chunked
kmp_nm_ord_static	ordered static unspecialized
kmp_nm_ord_dynamic_chunked
kmp_nm_ord_guided_chunked
kmp_nm_ord_runtime
kmp_nm_ord_auto	auto
kmp_nm_ord_trapezoidal
kmp_nm_upper	upper bound for nomerge values
kmp_sch_default	default scheduling algorithm

Definition at line 309 of file kmp.h.

---

Function Documentation

void __kmpc_critical	(	ident_t *	loc,
		kmp_int32	global_tid,
		kmp_critical_name *	crit
	)

Parameters:

	loc	source location information.
	global_tid	global thread number .
	crit	identity of the critical section. This could be a pointer to a lock associated with the critical section, or some other suitably unique value.

Enter code protected by a `critical` construct. This function blocks until the executing thread can enter the critical section.

Definition at line 1070 of file kmp_csupport.c.

References __kmp_acquire_user_lock_with_checks(), __kmp_env_consistency_check, __kmp_get_critical_section_ptr(), __kmp_push_sync(), __kmp_user_lock_kind, ct_critical, KA_TRACE, KC_TRACE, KMP_CHECK_USER_LOCK_INIT, kmp_tas_lock::lk, lk_tas, OMP_CRITICAL_SIZE, kmp_base_tas_lock::poll, and kmp_user_lock::tas.

Referenced by GOMP_critical_name_start(), and GOMP_critical_start().

void __kmpc_dispatch_init_4	(	ident_t *	loc,
		kmp_int32	gtid,
		enum sched_type	schedule,
		kmp_int32	lb,
		kmp_int32	ub,
		kmp_int32	st,
		kmp_int32	chunk
	)

Parameters:

	loc	Source location
	gtid	Global thread id
	schedule	Schedule type
	lb	Lower bound
	ub	Upper bound
	st	Step (or increment if you prefer)
	chunk	The chunk size to block with

This function prepares the runtime to start a dynamically scheduled for loop, saving the loop arguments. These functions are all identical apart from the types of the arguments.

Definition at line 2141 of file kmp_dispatch.cpp.

References __kmp_init_serial, and KMP_DEBUG_ASSERT.

void __kmpc_end_critical	(	ident_t *	loc,
		kmp_int32	global_tid,
		kmp_critical_name *	crit
	)

Parameters:

	loc	source location information.
	global_tid	global thread number .
	crit	identity of the critical section. This could be a pointer to a lock associated with the critical section, or some other suitably unique value.

Leave a critical section, releasing any lock that was held during its execution.

Definition at line 1121 of file kmp_csupport.c.

References __kmp_env_consistency_check, __kmp_pop_sync(), __kmp_release_user_lock_with_checks(), __kmp_user_lock_kind, ct_critical, KA_TRACE, KC_TRACE, KMP_ASSERT, kmp_tas_lock::lk, lk_tas, OMP_CRITICAL_SIZE, ompt_callbacks, ompt_status, ompt_status_track_callback, kmp_base_tas_lock::poll, kmp_user_lock::tas, and TCR_PTR.

Referenced by GOMP_critical_end(), and GOMP_critical_name_end().

void __kmpc_end_master	(	ident_t *	loc,
		kmp_int32	global_tid
	)

Parameters:

	loc	source location information.
	global_tid	global thread number .

Mark the end of a master region. This should only be called by the thread that executes the master region.

Definition at line 890 of file kmp_csupport.c.

References __kmp_env_consistency_check, __kmp_pop_sync(), __kmp_threads, __kmp_tid_from_gtid, ct_master, KC_TRACE, KMP_DEBUG_ASSERT, KMP_MASTER_GTID, KMP_WARNING, ompt_callbacks, ompt_status, ompt_status_track_callback, and kmp_team::t.

void __kmpc_end_ordered	(	ident_t *	loc,
		kmp_int32	gtid
	)

Parameters:

	loc	source location information.
	gtid	global thread number.

End execution of an ordered construct.

Definition at line 991 of file kmp_csupport.c.

References __kmp_parallel_dxo(), __kmp_threads, KC_TRACE, ompt_callbacks, ompt_status, and ompt_status_track_callback.

Referenced by GOMP_ordered_end().

void __kmpc_end_single	(	ident_t *	loc,
		kmp_int32	global_tid
	)

Parameters:

	loc	source location information
	global_tid	global thread number

Mark the end of a single construct. This function should only be called by the thread that executed the block of code protected by the `single` construct.

Definition at line 1303 of file kmp_csupport.c.

References __kmp_exit_single(), __kmp_threads, __kmp_tid_from_gtid, ompt_callbacks, ompt_status, ompt_status_track_callback, and kmp_team::t.

void __kmpc_for_static_fini	(	ident_t *	loc,
		kmp_int32	global_tid
	)

Parameters:

	loc	Source location
	global_tid	Global thread id

Mark the end of a statically scheduled loop.

Definition at line 1328 of file kmp_csupport.c.

References __kmp_env_consistency_check, __kmp_pop_workshare(), __kmp_threads, __kmp_tid_from_gtid, ct_pdo, KE_TRACE, ompt_callbacks, ompt_status, ompt_status_track_callback, and kmp_team::t.

void __kmpc_for_static_init_4	(	ident_t *	loc,
		kmp_int32	gtid,
		kmp_int32	schedtype,
		kmp_int32 *	plastiter,
		kmp_int32 *	plower,
		kmp_int32 *	pupper,
		kmp_int32 *	pstride,
		kmp_int32	incr,
		kmp_int32	chunk
	)

Parameters:

	loc	Source code location
	gtid	Global thread id of this thread
	schedtype	Scheduling type
	plastiter	Pointer to the "last iteration" flag
	plower	Pointer to the lower bound
	pupper	Pointer to the upper bound
	pstride	Pointer to the stride
	incr	Pointer to the increment
	chunk	Pointer to the chunk size

Each of the four functions here are identical apart from the argument types.

The functions compute the upper and lower bounds and stride to be used for the set of iterations to be executed by the current thread from the statically scheduled loop that is described by the initial values of the bround, stride, increment and chunk size.

Definition at line 346 of file kmp_sched.cpp.

void __kmpc_for_static_init_4u	(	ident_t *	loc,
		kmp_int32	gtid,
		kmp_int32	schedtype,
		kmp_int32 *	plastiter,
		kmp_uint32 *	plower,
		kmp_uint32 *	pupper,
		kmp_int32 *	pstride,
		kmp_int32	incr,
		kmp_int32	chunk
	)

See __kmpc_for_static_init_4

Definition at line 358 of file kmp_sched.cpp.

void __kmpc_for_static_init_8	(	ident_t *	loc,
		kmp_int32	gtid,
		kmp_int32	schedtype,
		kmp_int32 *	plastiter,
		kmp_int64 *	plower,
		kmp_int64 *	pupper,
		kmp_int64 *	pstride,
		kmp_int64	incr,
		kmp_int64	chunk
	)

See __kmpc_for_static_init_4

Definition at line 370 of file kmp_sched.cpp.

void __kmpc_for_static_init_8u	(	ident_t *	loc,
		kmp_int32	gtid,
		kmp_int32	schedtype,
		kmp_int32 *	plastiter,
		kmp_uint64 *	plower,
		kmp_uint64 *	pupper,
		kmp_int64 *	pstride,
		kmp_int64	incr,
		kmp_int64	chunk
	)

See __kmpc_for_static_init_4

Definition at line 382 of file kmp_sched.cpp.

kmp_int32 __kmpc_master	(	ident_t *	loc,
		kmp_int32	global_tid
	)

Parameters:

	loc	source location information.
	global_tid	global thread number .

Returns:

1 if this thread should execute the master block, 0 otherwise.

Definition at line 844 of file kmp_csupport.c.

References __kmp_check_sync(), __kmp_env_consistency_check, __kmp_init_parallel, __kmp_parallel_initialize(), __kmp_push_sync(), __kmp_threads, __kmp_tid_from_gtid, ct_master, KC_TRACE, KMP_MASTER_GTID, ompt_callbacks, ompt_status, ompt_status_track_callback, status, kmp_team::t, and TCR_4.

Referenced by __kmpc_barrier_master_nowait().

void __kmpc_ordered	(	ident_t *	loc,
		kmp_int32	gtid
	)

Parameters:

	loc	source location information.
	gtid	global thread number.

Start execution of an ordered construct.

Definition at line 926 of file kmp_csupport.c.

References __kmp_init_parallel, __kmp_init_serial, __kmp_parallel_deo(), __kmp_parallel_initialize(), __kmp_threads, KC_TRACE, KMP_DEBUG_ASSERT, ompt_callbacks, ompt_status, ompt_status_track, ompt_status_track_callback, and TCR_4.

Referenced by GOMP_ordered_start().

kmp_int32 __kmpc_single	(	ident_t *	loc,
		kmp_int32	global_tid
	)

Parameters:

	loc	source location information
	global_tid	global thread number

Returns:

One if this thread should execute the single construct, zero otherwise.

Test whether to execute a single construct. There are no implicit barriers in the two "single" calls, rather the compiler should introduce an explicit barrier if it is required.

Definition at line 1265 of file kmp_csupport.c.

References __kmp_enter_single(), __kmp_threads, __kmp_tid_from_gtid, ompt_callbacks, ompt_status, ompt_status_track_callback, kmp_team::t, and TRUE.