proter-root/com.workflowfm.proter.schedule/LookaheadScheduler

LookaheadScheduler

class LookaheadScheduler(initialTasks: TaskInstance*) extends PriorityScheduler

A Scheduler to be used for look-ahead.

Should be used in conjunction with simulations which use the lookahead trait.

Relies on the use of Schedules for each TaskResource.

class PriorityScheduler

trait Scheduler

class Object

trait Matchable

class Any

Value members

Concrete methods

Adds an Task described by an (ID,time) pair to the list of completed IDs

Definition Classes: Scheduler

@tailrec

Finds the TaskInstances that can be started now.

The algorithm is recursive, and works by starting with the original lookahead structure and slowly reducing it as the algorithm progresses. Every time a task is scheduled, the subsequent tasks are discovered via the lookahead structure and are added to the task list, while the structure itself removes these tasks such that a single task cannot be returned more than once.

TaskInstances are assumed to be sorted by priority.

Taking each TaskInstance from high to low priority, the algorithm does the following:

It merges the current Schedules of all the TaskResources involved in the Task.
It finds the earliest possible starting time of the TaskInstance in the merged Schedule, using the task's minimum starting time.
It finds the tasks that will start after the TaskInstance using the lookahead structure, and updates the structure.
Takes the interval defined by the starting time and the estimated duration of the TaskInstance and adds it to the Schedules of all the involved TaskResources.
If the starting time is equal to the current time, and all involved TaskResources are idle, it adds the TaskInstance to the result.

Value Params

currentTime: The current timestamp.
lookaheadSetThisIter: The lookahead structure to be used. Is reduced over time as tasks are scheduled.
resourceMap: The map of available TaskResources.
result: The accumulated TaskInstances so far (for tail recursion).
scheduledThisIter: The set of TaskInstances that have been scheduled so far and the times at which they are scheduled.
schedules: The map of Schedules for each TaskResource.
tasks: The set of TaskInstances that need to be considered.

Returns