Resource-constrained scheduling Flashcards
What are nonrenewable resources?
These are available on a total project basis, with a limited consumption availability for the entire project (money, energy, raw materials…)
What are renewable resources?
These are available on a period-by-period basis, i.e. the available amount is renewed from period to period. Only the total resource use at every time instant is constrained. (manpower, machines, tools, space, …)
When is a schedule feasible?
If the precedence and the renewable resource constraints are satisfied.
What does RCPSP stands for?
Resource Constraint Project Scheduling Problem: Resolving the conflicts of resources by shifting activities forward in time
How to schedule for maximizing the net present value?
Schedule the activities with a positive cash flow asap and the activities with a negative cash flow alap with respect to the precedence relations, resource constraints and the deadline.
For what projects can maximizing NPV be relevant?
Big projects with high capitals and long durations.
What is the lower bound of the duration of the critical chain?
The critical path
What does RLPSP stands for?
Resource Leveling Project Scheduling Problem: Trying to schedule a precedence and resource feasible schedule within a predefined deadline with a resource use that is as level as possible within the project horizon.
What does RCPSPDC stands for?
Resource Constrained Project Scheduling Problem Discounted Cash: Maximizing the NPV with respect to the precedence relations, resource use and deadline.
What does RCPSPDC stands for?
Resource Constrained Project Scheduling Problem Discounted Cash: Maximizing the NPV with respect to the precedence relations, resource use and deadline.
What is activity based priority rule?
Making a priority list based on characteristics of activities like duration.
What is network based priority rule?
Making a priority list based on the network logic, i.e. set of activities and their precedence relations.
What is critical path based priority rule?
Making a priority list using information from the critical path.
What is resource based priority rule?
Making a priority list based on the network logic and the resource information.
What does SSGS stands for?
Serial schedule generation scheme
What does PSGS stands for?
Parallel schedule generation scheme
What kinds of lower bounds are there?
- Critical path lower bound
- Resource based lower bound (sum of work content divided by total resources)
- Critical sequence lower bound (combination 1 and 2)
What types of cost are there?
Activity cost:
Fixed cost: Fixed amount independent of the duration and work content
Variable cost: cost per time unit dependent on the activity duration
Resource cost:
Cost per use: One time cost, independent
Cost per unit: Depends on quantity of resources
Fixed use: Quantity of resource is independent from duration
Variable use: Quantity varies with the duration
What’s the different between a chain and a path?
A path is always a series of activities in a network defined by precedence relations.
A chain is not always a path, it can be linked by precedence relations but also by resource relations!
The critical chain depends on:
- Your own choices or quality used software
- The available and used resources
- The project objective
What is the net present value?
Discounted value of money to the value it has today.
What is a lump sum payment?
Big payment at the end of a project that is an incentive to determine the project as soon as possible if the net present value is the objective of the project. Otherwise the project will be postponed too much. Due to the lump sum payment, time becomes also important even if the objective is not time!
Why is a lump sum payment needed?
To stimulate the contractor to finish the project in time as he will maximize the net present value.
How to construct STP priority list?
Shortest Processing Time:
- First make a list of the eligible activities
- Select activity with shortest duration time
- Update eligible list
- Repeat
NOTE: If duration is equal, choose lower ranking number
Why do we need lower bounds for scheduling?
Scheduling gives a heuristic solution, we can validate the quality by measuring the percentage deviation from a lower bound
