/src/wrappers/glib/library/core/g_thread_pool.e

  1indexing
  2	description: "Thread Pools — pools of threads to execute work concurrently"
  3	copyright: "(C) 2011 Paolo Redaelli"
  4	license: "LGPL v2 or later"
  5	version: "2.28"
  6
  7deferred class G_THREAD_POOL [A_ROUTINE -> G_POOLED_ROUTINE]
  8	obsolete "G_THREAD_POOL is currently unusable because standard library is NOT thread safe. At all"
  9	-- A pool of threads executing A_ROUTINE concurrently.
 10
 11	-- Sometimes you wish to asynchronously fork out the execution of work and
 12	-- continue working in your own thread. If that will happen often, the
 13	-- overhead of starting and destroying a thread each time might be too
 14	-- high. In such cases reusing already started threads seems like a good
 15	-- idea. And it indeed is, but implementing this can be tedious and
 16	-- error-prone.
 17
 18	-- Therefore GLib provides thread pools for your convenience. An added
 19	-- advantage is, that the threads can be shared between the different
 20	-- subsystems of your program, when they are using GLib.
 21
 22	-- To create a new thread pool, you use `make'. 
 23
 24 	-- If you want to execute a certain task within a thread pool, you call `push'.
 25
 26	-- To get the current number of running threads you call `threads_count'.
 27	-- To get the number of still unprocessed tasks you call
 28	-- `unprocessed_count'. To control the maximal number of threads for a
 29	-- thread pool, you use `max_threads' and `set_max_threads`.
 30
 31	-- Finally you can control the number of unused threads, that are kept
 32	-- alive by GLib for future use. The current number can be fetched with
 33	-- `unused_threads_count'. The maximal number can be controlled by
 34	-- `max_unused_threads' and `set_max_unused_threads'. All currently unused
 35	-- threads can be stopped by calling `stop_unused_threads`.
 36
 37	-- Note for Liberty users: 
 38inherit 
 39	WRAPPER 
 40		-- A thread pool should be "EIFFEL_OWNED redefine dispose end", but since EIFFEL_OWNED contains only a simplicistic definition of `dispose' it is actully cleaner just to define dispose here.
 41
 42	FACTORY[A_ROUTINE] rename new as new_routine end
 43
 44insert 
 45	GTHREADPOOL_EXTERNALS
 46	GTHREAD_EXTERNALS
 47
 48feature {} -- Creation
 49	make (a_max_threads_count: INTEGER; is_exclusive: BOOLEAN;) is
 50		-- Creation command of a new thread pool.
 51
 52		-- Whenever you call `push', either a new thread is created or an
 53		-- unused one is reused . At most a_max_threads_count threads are
 54		-- running concurrently for this thread pool. `a_max_threads_count' = -1 allows
 55		-- unlimited threads to be created for this thread pool. 
 56
 57		-- The newly created or reused thread now executes A_ROUTINE.command with a reference to Current G_THREAD_POOL.
 58		
 59		-- `is_exclusive' determines, whether the thread pool owns all threads
 60		-- exclusive or whether the threads are shared globally. If
 61		-- `is_exclusive' is True, `a_max_threads_count' threads are started immediately
 62		-- and they will run exclusively for this thread pool until it is
 63		-- destroyed by dispose. If `is_exclusive' is False, threads
 64		-- are created, when needed and shared between all non-exclusive thread
 65		-- pools. This implies that `a_max_threads_count' may not be -1 for exclusive
 66		-- thread pools.
 67		
 68		-- TODO: provide GError support ("..error can be NULL to ignore errors, or non-NULL to report errors. An error can only occur when exclusive is set to TRUE and not all max_threads threads could be created..")
 69	local self: like Current; a_routine: like new_routine
 70	do
 71		g_thread_init(default_pointer)
 72		self := Current
 73		a_routine := new_routine
 74		from_external_pointer(g_thread_pool_new(a_routine.invoke_address, $self, a_max_threads_count, is_exclusive.to_integer, 
 75		default_pointer -- could be GError **error);
 76		))
 77	end
 78
 79feature -- Commands
 80	push (some_data: like new_routine) is
 81		-- Inserts data into the list of tasks to be executed by pool. When the
 82		-- number of currently running threads is lower than the maximal
 83		-- allowed number of threads, a new thread is started (or reused) with
 84		-- the properties given to `make'. Otherwise data stays in
 85		-- the queue until a thread in this pool finishes its previous task and
 86		-- processes data.
 87
 88		-- TODO: add GError support "error can be NULL to ignore errors, or non-NULL to report errors. An
 89		-- error can only occur when a new thread couldn't be created. In that
 90		-- case data is simply appended to the queue of work to do."
 91	local a_data: like new_routine
 92	do
 93		a_data := some_data -- this step is needed to circumvent a limitation of SmartEiffel $ operator
 94		g_thread_pool_push
 95		(handle, $a_data,
 96		default_pointer -- could be GError **error);
 97		)
 98	end
 99
100	set_max_threads (a_number: INTEGER) is
101	-- Sets the maximal allowed number of threads for pool. A value of -1 means, that the maximal number of threads is unlimited.
102
103	-- Setting max_threads to 0 means stopping all work for pool. It is effectively frozen until max_threads is set to a non-zero value again.
104	-- 
105	-- A thread is never terminated while calling func, as supplied by g_thread_pool_new(). Instead the maximal number of threads only has effect for the allocation of new threads in g_thread_pool_push(). A new thread is allocated, whenever the number of currently running threads in pool is smaller than the maximal number.
106	-- 
107	-- error can be NULL to ignore errors, or non-NULL to report errors. An error can only occur when a new thread couldn't be created.
108	-- 
109	do
110		g_thread_pool_set_max_threads (handle, a_number, default_pointer -- could be GError **error);
111		)
112	end
113
114feature -- Disposing
115	dispose is
116		--Frees all resources allocated for pool.
117
118		-- If immediate is TRUE, no new task is processed for pool. Otherwise pool is not freed before the last task is processed. Note however, that no thread of this pool is interrupted, while processing a task. Instead at least all still running threads can finish their tasks before the pool is freed.
119
120		-- If wait_ is TRUE, the functions does not return before all tasks to be processed (dependent on immediate, whether all or only the currently running) are ready. Otherwise the function returns immediately.
121
122		-- After calling this function pool must not be used anymore.
123	do
124		g_thread_pool_free (handle, 0 -- gboolean immediate
125		, 1 -- gboolean wait_
126		)
127		-- immediate :	should pool shut down immediately?
128		-- wait_ : should the function wait for all tasks to be finished?
129	end
130
131	set_max_unused_threads (a_maximum: INTEGER_32) is
132		-- Sets the maximal number of unused threads to `a_maximum'. If it is
133		-- -1, no limit is imposed on the number of unused threads.
134	do
135		g_thread_pool_set_max_unused_threads(a_maximum)
136	end
137
138	stop_unused_threads is
139		-- Stops all currently unused threads. This does not change the maximal
140		-- number of unused threads. This function can be used to regularly
141		-- stop all unused threads e.g. from g_timeout_add().
142	do
143		g_thread_pool_stop_unused_threads 
144	end
145
146	set_max_idle_time (an_interval: NATURAL_32) is
147		-- Set to `an_interval' the maximum interval (in 1/1000ths of a second)
148		-- that a thread waiting in the pool for new tasks can be idle for
149		-- before being stopped. This command is similar to invoking
150		-- `stop_unused_threads' on a regular timeout, except, this is done on
151		-- a per thread basis.
152
153		-- By setting interval to 0, idle threads will not be stopped.
154		-- (Low-level note: this function makes use of
155		-- g_async_queue_timed_pop() using interval).
156	do
157		g_thread_pool_set_max_idle_time (an_interval)
158	end
159
160feature -- Queries
161	exit_immidiatly: BOOLEAN is
162		-- 
163		attribute
164	end
165
166	does_exit_on_dispose: BOOLEAN is
167		--
168		attribute
169	end
170	
171	max_threads: INTEGER is
172		-- The maximum number of threads in Current pool
173	do
174		Result:=g_thread_pool_get_max_threads (handle)
175	end
176
177	threads_count: NATURAL_32 is
178		-- The number of threads currently running in the pool
179	do
180		Result := g_thread_pool_get_num_threads (handle)
181	end
182
183 	unprocessed_count: NATURAL_32 is
184		-- The number of tasks still unprocessed in the pool
185	do
186		Result := g_thread_pool_unprocessed (handle)
187	end 
188
189	max_unused_threads: INTEGER is
190		-- The maximal allowed number of unused threads
191	do
192		Result:=g_thread_pool_get_max_unused_threads
193	end
194
195	unused_threads_count: NATURAL_32 is
196		-- the number of currently unused threads.
197	do
198		Result := g_thread_pool_get_num_unused_threads
199	end
200
201	max_idle_time: NATURAL_32 is
202		-- the maximum interval to wait for new tasks in the thread pool before stopping the thread (1/1000ths of a second).
203		-- When 0, threads waiting in the thread pool for new work are not stopped.
204	do
205		Result := g_thread_pool_get_max_idle_time 
206	end
207feature {} -- Unwrapped
208-- 	void                g_thread_pool_set_sort_function     (GThreadPool *pool,
209--                                                          GCompareDataFunc func,
210--                                                          gpointer user_data);
211-- 
212-- Sets the function used to sort the list of tasks. This allows the tasks to be processed by a priority determined by func, and not just in the order in which they were added to the pool.
213-- 
214-- Note, if the maximum number of threads is more than 1, the order that threads are executed can not be guranteed 100%. Threads are scheduled by the operating system and are executed at random. It cannot be assumed that threads are executed in the order they are created.
215-- 
216-- pool :
217-- 	a GThreadPool
218-- 
219-- func :
220-- 	the GCompareDataFunc used to sort the list of tasks. This function is passed two tasks. It should return 0 if the order in which they are handled does not matter, a negative value if the first task should be processed before the second or a positive value if the second task should be processed first.
221end -- class G_THREAD_POOL