stapl::runtime::context Class Reference

Execution context of a task or request. More...

Public Member Functions
	context (id const &cid, location_md &l, const process_id src_pid)
	Constructs a new context object from the given id and associates it with the metadata.
	context (location_md &l)
	Constructs a new context object from the given metadata. More...
	~context (void)
	Destroys this context object. More...
	context (context const &)=delete
context &	operator= (context const &)=delete
id const &	get_id (void) const noexcept
full_location const &	get_initiator (void) const noexcept
	Returns the gang id and location id as a full_location object that created this context object.
full_location const &	get_current_location (void) const noexcept
	Returns the gang id and location id associated with this context as a full_location object.
gang_md const &	get_gang_md (void) const noexcept
gang_md &	get_gang_md (void) noexcept
location_md const &	get_location_md (void) const noexcept
location_md &	get_location_md (void) noexcept
gang_md::id	get_gang_id (void) const noexcept
location_md::id	get_location_id (void) const noexcept
process_id	get_source_process_id (void) const noexcept
bool	is_intragang (void) const noexcept
nesting_level	get_nesting (void) const noexcept
bool	is_base (void) const noexcept
void	set_epoch (const epoch_type e)
	Sets the epoch this context is in. More...
epoch_type	get_epoch (void) const noexcept
void *	allocate_return (const std::size_t size)
	Allocates space for a return value request.
aggregator_type &	get_aggregator (full_location const &loc)
	Returns a request aggregator to the given destination. More...
void	flush_requests (void)
	Flushes all aggregated requests.
void	flush (void)
	Flushes all aggregated requests and fence metadata.
void	count_pending (full_location const &loc)
	Increases the count of pending buffers. More...
void	count_pending (const gang_md::id dst_gid, const unsigned int N)
	Increases the count of pending buffers by N. More...
void	count_processed (void)
	Increases the count of processed buffers. More...

Public Types
using	id = context_id
using	aggregator_type = context_impl::aggregator
using	epoch_type = logical_clock::time_type

Detailed Description

Execution context of a task or request.

All tasks and requests execute within a context defined by a context object. Each context has a unique context_id object that acts as its id.

Contexts of a new execution environment are called base contexts. A base context is not created by a request and therefore it has a nesting level of 0 and mirrors the epoch of the associated location_md object.

Every other context is created as the result of executing requests and they have nesting level that is that of the request source + 1 and mirror the epoch of the calling context.

Imposing an ordering between contexts is the backbone of request ordering. Each context object is associated with a queue of requests which will execute in a FIFO order. Therefore, changing the ordering of context objects changes the request execution order.

See also

context_id, gang_md, location_md

Constructor & Destructor Documentation

context()

stapl::runtime::context::context ( location_md &  l )

explicit

Constructs a new context object from the given metadata.

This is base context, meaning that it executes code that was not triggered by a request. It will be pushed on the stack automatically.

~context()

stapl::runtime::context::~context

(

void

)

Destroys this context object.

All requests and metadata will be flushed. In the case that it was a base context, then it will be removed from the stack automatically.

Member Function Documentation

set_epoch()

void stapl::runtime::context::set_epoch

(

const epoch_type

e

)

Sets the epoch this context is in.

If epoch differs from the previous, requests will be flushed.

get_aggregator()

aggregator_type& stapl::runtime::context::get_aggregator

(

full_location const &

loc

)

Returns a request aggregator to the given destination.

The aggregator from the previous call to get_aggregator() is memoized unless flush() has been called.

Warning

While memoization may have a positive effect when a location communicates with the same location repeatedly, it may have no or negative performance effects under a less repeated communication pattern.

If the gang metadata is not known, requests are sent to the owner process of the destination gang id, which always knows where to forward them. This can potentially create a choking point.

count_pending() [1/2]

void stapl::runtime::context::count_pending

(

full_location const &

loc

)

Increases the count of pending buffers.

This function is called when the destination of the requests in the buffer is loc.

count_pending() [2/2]

void stapl::runtime::context::count_pending	(	const gang_md::id	dst_gid,
		const unsigned int	N
	)

Increases the count of pending buffers by N.

This function is called when the destination of the requests in the buffer is some or all locations in gang dst_gid.

count_processed()

void stapl::runtime::context::count_processed

(

void

)

Increases the count of processed buffers.

This function flushes the buffer containing return values, since blocking calls may be waiting for them.

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

• context.hpp
• context.cc