activity-term.hpp File Reference

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Description

A term of the activity language describing interconnected scheduler activities.

The activity::Term is created as a transient object in builder notation, and used to lay out the specifics of the planned operations necessary to calculate a single frame or to carry out some administrative task. The actual Activity verbs are allocated independently, within the BlockFlow allocation scheme, while the Term links and configures these data records and prepares them to instruct the Scheduler. Through the activity::Term, relevant attachment points are exposed for configuration, yet after posting the entrance point of an activity chain to the Scheduler, the term is obsoleted and can be discarded without affecting the individual Activities awaiting activation through the Scheduler.

Wiring schemes

The »mechanics« of render activities are considered finite, and cohesive low-level code. Thus only a limited selection of wiring schemes is provided, offering just enough leeway to implement the foreseeable variations in functionality. The underlying operational sequence is as follows

• as entrance point, the complete chain of activities is posted, thereby defining a start time and deadline window; moreover this indirection ensures that the following execution until WORKSTART happens in »management mode«, which is performed single threaded and may alter the scheduler queue (enqueue, dequeue).
• optionally, a GATE can enforce the deadline and block until a predetermined number of prerequisite notifications has been received
• next follows the actual job invocation, which is bracketed in WORKSTART and WORKSTOP
• the actual job invocation relies on two additional FEED records to hold parameters
• at the end of the chain, optionally a NOTIFY can be appended and linked to the GATE of a follow-up job, which thereby becomes dependent on this actual job's completion.

While the regular media computation job employs this complete scheme, the Template::META_JOB uses the minimal setup, comprised only of post and invocation (since the meta job is used for planning further jobs and thus entirely in »management mode« and without further inhibitions or notifications). Another variation is presented by the Template::LOAD_JOB, which enables the integration of asynchronous IO. The actual JobFunctor in this case is assumed just to dispatch a long running external IO operation and then return quickly. Upon completion of the external work, a callback will be activated, which must be wired such as to re-activate the rest of the activities. Consequently for this mode of operation the activity chain becomes severed into two segments, cutting right behind the last FEED-Activity (i.e. after issuing the Job) but before the WORKSTOP. The callback then dispatches the WORKSTOP and possibly a chained NOTIFY.

See also

SchedulerActivity_test

activity-lang.hpp Entrance point to Activity definition

activity.hpp definition of verbs

Definition in file activity-term.hpp.

#include "vault/gear/activity.hpp"
#include "vault/gear/block-flow.hpp"
#include "vault/gear/job.h"
#include "lib/time/timevalue.hpp"
#include <string>
#include <utility>

Classes
class	Term
	A Term of the »Activity Language«, describing the steps necessary to perform the calculation of a single frame or similar tasks. More...

Namespaces
	vault
	Vault-Layer implementation namespace root.
	vault::gear
	Active working gear and plumbing.