StarPU Handbook
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Typedefs | |
typedef uint64_t | starpu_tag_t |
Functions | |
void | starpu_task_declare_deps_array (struct starpu_task *task, unsigned ndeps, struct starpu_task *task_array[]) |
void | starpu_tag_declare_deps (starpu_tag_t id, unsigned ndeps,...) |
void | starpu_tag_declare_deps_array (starpu_tag_t id, unsigned ndeps, starpu_tag_t *array) |
int | starpu_tag_wait (starpu_tag_t id) |
int | starpu_tag_wait_array (unsigned ntags, starpu_tag_t *id) |
void | starpu_tag_restart (starpu_tag_t id) |
void | starpu_tag_remove (starpu_tag_t id) |
void | starpu_tag_notify_from_apps (starpu_tag_t id) |
This type defines a task logical identifer. It is possible to associate a task with a unique tag chosen by the application, and to express dependencies between tasks by the means of those tags. To do so, fill the field starpu_task::tag_id with a tag number (can be arbitrary) and set the field starpu_task::use_tag to 1. If starpu_tag_declare_deps() is called with this tag number, the task will not be started until the tasks which holds the declared dependency tags are completed.
void starpu_task_declare_deps_array | ( | struct starpu_task * | task, |
unsigned | ndeps, | ||
struct starpu_task * | task_array[] | ||
) |
Declare task dependencies between a task
and an array of tasks of length ndeps
. This function must be called prior to the submission of the task, but it may called after the submission or the execution of the tasks in the array, provided the tasks are still valid (i.e. they were not automatically destroyed). Calling this function on a task that was already submitted or with an entry of task_array
that is no longer a valid task results in an undefined behaviour. If ndeps
is 0, no dependency is added. It is possible to call starpu_task_declare_deps_array() several times on the same task, in this case, the dependencies are added. It is possible to have redundancy in the task dependencies.
void starpu_tag_declare_deps | ( | starpu_tag_t | id, |
unsigned | ndeps, | ||
... | |||
) |
Specify the dependencies of the task identified by tag id
. The first argument specifies the tag which is configured, the second argument gives the number of tag(s) on which id
depends. The following arguments are the tags which have to be terminated to unlock the task. This function must be called before the associated task is submitted to StarPU with starpu_task_submit().
WARNING! Use with caution. Because of the variable arity of starpu_tag_declare_deps(), note that the last arguments must be of type starpu_tag_t : constant values typically need to be explicitly casted. Otherwise, due to integer sizes and argument passing on the stack, the C compiler might consider the tag 0x200000003
instead of 0x2
and 0x3
when calling starpu_tag_declare_deps(0x1, 2, 0x2, 0x3)
. Using the starpu_tag_declare_deps_array() function avoids this hazard.
void starpu_tag_declare_deps_array | ( | starpu_tag_t | id, |
unsigned | ndeps, | ||
starpu_tag_t * | array | ||
) |
This function is similar to starpu_tag_declare_deps(), except that its does not take a variable number of arguments but an array of tags of size ndeps
.
int starpu_tag_wait | ( | starpu_tag_t | id | ) |
This function blocks until the task associated to tag id
has been executed. This is a blocking call which must therefore not be called within tasks or callbacks, but only from the application directly. It is possible to synchronize with the same tag multiple times, as long as the starpu_tag_remove() function is not called. Note that it is still possible to synchronize with a tag associated to a task for which the strucuture starpu_task was freed (e.g. if the field starpu_task::destroy was enabled).
int starpu_tag_wait_array | ( | unsigned | ntags, |
starpu_tag_t * | id | ||
) |
This function is similar to starpu_tag_wait() except that it blocks until all the ntags
tags contained in the array id
are terminated.
void starpu_tag_restart | ( | starpu_tag_t | id | ) |
This function can be used to clear the already notified status of a tag which is not associated with a task. Before that, calling starpu_tag_notify_from_apps() again will not notify the successors. After that, the next call to starpu_tag_notify_from_apps() will notify the successors.
void starpu_tag_remove | ( | starpu_tag_t | id | ) |
This function releases the resources associated to tag id
. It can be called once the corresponding task has been executed and when there is no other tag that depend on this tag anymore.
void starpu_tag_notify_from_apps | ( | starpu_tag_t | id | ) |
This function explicitly unlocks tag id
. It may be useful in the case of applications which execute part of their computation outside StarPU tasks (e.g. third-party libraries). It is also provided as a convenient tool for the programmer, for instance to entirely construct the task DAG before actually giving StarPU the opportunity to execute the tasks. When called several times on the same tag, notification will be done only on first call, thus implementing "OR" dependencies, until the tag is restarted using starpu_tag_restart().