/*
 * This file is part of the StarPU Handbook.
 * Copyright (C) 2009--2011  Universit@'e de Bordeaux 1
 * Copyright (C) 2010, 2011, 2012, 2013  Centre National de la Recherche Scientifique
 * Copyright (C) 2011, 2012 Institut National de Recherche en Informatique et Automatique
 * See the file version.doxy for copying conditions.
 */

/*! \defgroup API_Scheduling_Policy Scheduling Policy

\brief TODO. While StarPU comes with a variety of scheduling policies
(see \ref TaskSchedulingPolicy), it may sometimes be desirable to
implement custom policies to address specific problems. The API
described below allows users to write their own scheduling policy.

\struct starpu_sched_policy
\ingroup API_Scheduling_Policy
This structure contains all the methods that implement a
scheduling policy. An application may specify which scheduling
strategy in the field starpu_conf::sched_policy passed to the function
starpu_init().
\var starpu_sched_policy::init_sched
        Initialize the scheduling policy.
\var starpu_sched_policy::deinit_sched
        Cleanup the scheduling policy.
\var starpu_sched_policy::push_task
        Insert a task into the scheduler.
\var starpu_sched_policy::push_task_notify
        Notify the scheduler that a task was pushed on a given worker.
	This method is called when a task that was explicitely
	assigned to a worker becomes ready and is about to be executed
	by the worker. This method therefore permits to keep the state
	of the scheduler coherent even when StarPU bypasses the
	scheduling strategy.
\var starpu_sched_policy::pop_task
        Get a task from the scheduler. The mutex associated to the
	worker is already taken when this method is called. If this
	method is defined as NULL, the worker will only execute tasks
	from its local queue. In this case, the push_task method
	should use the starpu_push_local_task method to assign tasks
	to the different workers.
\var starpu_sched_policy::pop_every_task
        Remove all available tasks from the scheduler (tasks are
	chained by the means of the field starpu_task::prev and
	starpu_task::next). The mutex associated to the worker is
	already taken when this method is called. This is currently
	not used.
\var starpu_sched_policy::pre_exec_hook
        Optional field. This method is called every time a task is starting.
\var starpu_sched_policy::post_exec_hook
        Optional field. This method is called every time a task has been executed.
\var starpu_sched_policy::add_workers
        Initialize scheduling structures corresponding to each worker used by the policy.
\var starpu_sched_policy::remove_workers
        Deinitialize scheduling structures corresponding to each worker used by the policy.
\var starpu_sched_policy::policy_name
        Optional field. Name of the policy.
\var starpu_sched_policy::policy_description
        Optional field. Human readable description of the policy.

\fn struct starpu_sched_policy **starpu_sched_get_predefined_policies()
\ingroup API_Scheduling_Policy
Return an NULL-terminated array of all the predefined scheduling
policies.

\fn void starpu_worker_get_sched_condition(int workerid, starpu_pthread_mutex_t **sched_mutex, starpu_pthread_cond_t **sched_cond)
\ingroup API_Scheduling_Policy
When there is no available task for a worker, StarPU blocks this
worker on a condition variable. This function specifies which
condition variable (and the associated mutex) should be used to block
(and to wake up) a worker. Note that multiple workers may use the same
condition variable. For instance, in the case of a scheduling strategy
with a single task queue, the same condition variable would be used to
block and wake up all workers.

\fn void starpu_sched_ctx_set_policy_data(unsigned sched_ctx_id, void *policy_data)
\ingroup API_Scheduling_Policy
Each scheduling policy uses some specific data (queues, variables,
additional condition variables). It is memorize through a local
structure. This function assigns it to a scheduling context.

\fn void *starpu_sched_ctx_get_policy_data(unsigned sched_ctx_id)
\ingroup API_Scheduling_Policy
Returns the policy data previously assigned to a context

\fn int starpu_sched_set_min_priority(int min_prio)
\ingroup API_Scheduling_Policy
Defines the minimum task priority level supported by the scheduling
policy. The default minimum priority level is the same as the default
priority level which is 0 by convention. The application may access
that value by calling the function starpu_sched_get_min_priority().
This function should only be called from the initialization method of
the scheduling policy, and should not be used directly from the
application.

\fn int starpu_sched_set_max_priority(int max_prio)
\ingroup API_Scheduling_Policy
Defines the maximum priority level supported by the scheduling policy.
The default maximum priority level is 1. The application may access
that value by calling the function starpu_sched_get_max_priority().
This function should only be called from the initialization method of
the scheduling policy, and should not be used directly from the
application.

\fn int starpu_sched_get_min_priority(void)
\ingroup API_Scheduling_Policy
Returns the current minimum priority level supported by the scheduling
policy

\fn int starpu_sched_get_max_priority(void)
\ingroup API_Scheduling_Policy
Returns the current maximum priority level supported by the scheduling
policy

\fn int starpu_push_local_task(int workerid, struct starpu_task *task, int back)
\ingroup API_Scheduling_Policy
The scheduling policy may put tasks directly into a worker’s local
queue so that it is not always necessary to create its own queue when
the local queue is sufficient. If \p back is not 0, \p task is put
at the back of the queue where the worker will pop tasks first.
Setting \p back to 0 therefore ensures a FIFO ordering.

\fn int starpu_push_task_end(struct starpu_task *task)
\ingroup API_Scheduling_Policy
This function must be called by a scheduler to notify that the given
task has just been pushed.

\fn int starpu_worker_can_execute_task(unsigned workerid, struct starpu_task *task, unsigned nimpl)
\ingroup API_Scheduling_Policy
Check if the worker specified by workerid can execute the codelet.
Schedulers need to call it before assigning a task to a worker,
otherwise the task may fail to execute.

\fn double starpu_timing_now(void)
\ingroup API_Scheduling_Policy
Return the current date in micro-seconds.

\fn uint32_t starpu_task_footprint(struct starpu_perfmodel *model, struct starpu_task *task, enum starpu_perfmodel_archtype arch, unsigned nimpl)
\ingroup API_Scheduling_Policy
Returns the footprint for a given task

\fn double starpu_task_expected_length(struct starpu_task *task, enum starpu_perfmodel_archtype arch, unsigned nimpl)
\ingroup API_Scheduling_Policy
Returns expected task duration in micro-seconds.

\fn double starpu_worker_get_relative_speedup(enum starpu_perfmodel_archtype perf_archtype)
\ingroup API_Scheduling_Policy
Returns an estimated speedup factor relative to CPU speed

\fn double starpu_task_expected_data_transfer_time(unsigned memory_node, struct starpu_task *task)
\ingroup API_Scheduling_Policy
Returns expected data transfer time in micro-seconds.

\fn double starpu_data_expected_transfer_time(starpu_data_handle_t handle, unsigned memory_node, enum starpu_data_access_mode mode)
\ingroup API_Scheduling_Policy
Predict the transfer time (in micro-seconds) to move \p handle to a memory node

\fn double starpu_task_expected_power(struct starpu_task *task, enum starpu_perfmodel_archtype arch, unsigned nimpl)
\ingroup API_Scheduling_Policy
Returns expected power consumption in J

\fn double starpu_task_expected_conversion_time(struct starpu_task *task, enum starpu_perfmodel_archtype arch, unsigned nimpl)
\ingroup API_Scheduling_Policy
Returns expected conversion time in ms (multiformat interface only)

\fn int starpu_get_prefetch_flag(void)
\ingroup API_Scheduling_Policy
Whether \ref STARPU_PREFETCH was set

\fn int starpu_prefetch_task_input_on_node(struct starpu_task *task, unsigned node)
\ingroup API_Scheduling_Policy
Prefetch data for a given task on a given node

*/
