How to implement Auto delay until last mode in PlanningListVariables

[kentbill]

Hi, Teams.

In the Chained Through Time pattern, when a task requires two employees to work together simultaneously, it's necessary to build on the Chained Through Time pattern with "automatic delay until last" logic to ensure both employees are available when the task starts.

I'm using PlanningListVariable with Shadow Variable in my project now. How should I implement logic - "automatic delay until last"? Should I implement this logic in the startTimeSupplier method, but I'm still unsure how to implement it? Do you have any ideas or implementation suggestions for this situation?

Thanks in advanced

About the automatic delay until last.
https://docs.timefold.ai/timefold-solver/latest/design-patterns/design-patterns#chainedThroughTimePattern

[Christopher-Chianelli]

You would divide the task into subtasks, and have the subtasks refer to each other inside a collection of required concurrent tasks.
You can then reference the required concurrent tasks inside your @ShadowSources.

Typically, a task would have a ready time (earilest possible start time), start time, and an end time. Ready time only depends on previous' end time, end time only depends on start time, and start time depends on ready time and the concurrent group's ready times.

For an example, see

timefold-solver/core/src/test/java/ai/timefold/solver/core/testdomain/shadow/concurrent/TestdataConcurrentValue.java

Lines 121 to 164 in f47b08f

	@ShadowSources({ "previousValue.serviceFinishTime", "entity" })
	public LocalDateTime serviceReadyTimeUpdater() {
	if (previousValue != null) {
	return previousValue.serviceFinishTime.plusMinutes(30L);
	}
	if (entity != null) {
	return BASE_START_TIME;
	}
	return null;
	}
	@ShadowSources(
	value = { "serviceReadyTime", "concurrentValueGroup[].serviceReadyTime" },
	alignmentKey = "concurrentValueGroup")
	public LocalDateTime serviceStartTimeUpdater() {
	if (isInconsistent) {
	throw new IllegalStateException(
	"Value (%s) is inconsistent when serviceStartTimeUpdater is called.".formatted(this));
	}
	if (serviceReadyTime == null) {
	return null;
	}
	var startTime = serviceReadyTime;
	if (concurrentValueGroup != null) {
	for (var visit : concurrentValueGroup) {
	if (visit.isInconsistent) {
	throw new IllegalStateException(
	"Value (%s) is inconsistent when serviceStartTimeUpdater is called.".formatted(visit));
	}
	if (visit.serviceReadyTime != null && startTime.isBefore(visit.serviceReadyTime)) {
	startTime = visit.serviceReadyTime;
	}
	}
	}
	return startTime;
	}
	@ShadowSources("serviceStartTime")
	public LocalDateTime serviceFinishTimeUpdater() {
	if (serviceStartTime == null) {
	return null;
	}
	return serviceStartTime.plusMinutes(30L);
	}

[kentbill]

Thank you! @Christopher-Chianelli