Schedule

Tasks and resources form a schedule. The cp_schedule method allows to optimize a schedule with respect to any objective variable and implements advanced scheduling techniques specialized in makespan minimization. The creation of the schedule makespan can be automated by calling the getmakespan method that ensures automatically its computation.

A custom scheduling optimization strategy can be specified by using the task_serialize branching scheme to select the task to be scheduled and value choice heuristics for its start and duration variables.

The task selection method can be any user Mosel method or it may be configured with the predefined strategies of Xpress Kalis:

The picture below illustrates the definition of a task-based branching strategy:

Xpress Kalis defines a set of functions for accessing and modifying cptask and cpresource states:

addpredecessors	Adds a set of predecessors for a task
addsuccessors	Adds a set of tasks as successors of a task
consumes	Sets the minimal and maximal amount of resource consumed by a task for a particular resource
cp_close_schedule	Close the schedule.
cp_get_default_schedule_strategy	Gets the default schedule search strategy of cp_schedule
cp_schedule	Optimizes the schedule with respect to an objective variable.
cp_set_schedule_strategy	Sets the schedule search strategy for cp_schedule
cp_show_schedule	Shows a textual representation of the current schedule
getassignment	Gets the cpvar representing the assignment of a task for a particular resource.
getcapacity	Get the maximal capacity of a resource for a specific time period.
getconsumption	Gets the cpvar representing the consumption of a task for a particular resource
getduration	Gets the cpvar representing a task duration
getend	Gets the cpvar representing a task completion time
getmakespan	Gets the cpvar representing the makespan of the schedule.
getproduction	Gets the cpvar representing the production of a task for a particular resource
getprovision	Gets the cpvar representing the provision of a task for a particular resource
getrequirement	Gets the cpvar representing the requirement of a task for a particular resource
getsetuptime	Gets the sequence dependent setup times between two tasks
getstart	Gets the cpvar representing a task start time
has_assignment	Tests whether an assignment decision variable for a task and a particular resource exists.
is_consuming	Tests whether a task consumes a specific resource
is_fixed	Tests if the variable passed in argument is instantiated
is_idletime	Tests if a timestep is an idle timestep for a resource.
is_producing	Tests whether a task produces a specific resource
is_providing	Tests whether a task provides a specific resource
is_requiring	Tests whether a task requires a specific resource
produces	Sets the minimal and maximal amount of resource produced by a task for a particular resource
provides	Sets the minimal and maximal amount of resource provided by a task for a particular resource.
requires	Sets the minimal and maximal amount of resource required by a task for a particular resource
resusage	Creates a resource usage
set_resource_attributes	Sets some attributes for a resource
set_task_attributes	Sets some attributes for a task
setcapacity	Sets the maximal capacity of a resource between two time bounds.
setduration	Sets the duration of a task
setidletimes	Specifies the set of timesteps where a resource is idle.
setmaxavailability	Sets the maximal capacity of a resource between two time bounds.
setminusage	Sets the minimum usage of a resource between two time bounds.
setpredecessors	Sets the tasks that must precede a task
setsetuptime	Sets sequence dependent setup times between two tasks
setsuccessors	Sets the set of tasks that must succeed a task

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Schedule