| Units: | - |
| Default Value: | 0 |
| Validation Rule: | ≥-1 |
| Description: | Number of years solved in each step of LT Plan |
The default behavior of LT Plan is to
optimize the entire planning horizon in one 'step', and this is the
ideal solution. However, for very large models it might be necessary
to break the optimization into multiple steps or to resolve the
horizon progressively using Rolling Horizon. The method used is
controlled by the Overlap setting
combined with At a Time.
- Multi-step
-
For the multi-step method, this option controls the number of
years solved in each step. A value of '0' means that the entire
horizon is solved in one step.
Note that you must select a number of
years that divides the years in the planning horizon precisely.
For example, the following combinations are valid:
- Solve 30 years in 3 steps of 10 years
- Solve 21 years in 3 steps of 7 years
The following are not valid:
- Solve 30 years in 4 steps
- Solve 20 years in 3 steps
- Rolling Horizon
- For the Rolling Horizon method, this option decides the length of
each 'roll'. For example if you set At a Time = 5 then each solve
will have full temporal resolution for five years and rolling will
occur every four years (one year is discarded from each roll by
default). For a 20 year horizon with At a Time = 5 the following
rolling steps are performed:
- Years 1-20 with full detail in years 1-5 and less detail in
years 6-20
- Years 5-20 with full detail in years 5-9 and less detail in
years 10-20 and optimal build decisions for years 1-4 from the
previous solution
- Years 10-20 with full detail in years 10-14 and less details
in year 15-20 and optimal build decisions for years 1-9 from the
previous solutions
- Years 15-20 with full detail in years 15-19 and less detail in
year 20 and optimal build decisions for years 1-14 from the
previous solutions
- Year 20 with full detail and optimal build decisions for years
1-19 from the previous solutions
- A final full detail run with all build decisions locked.
Note that these methods work independently of the Chronology
setting, meaning you can further reduce the computational burden of
the simulation by choosing Partial, Fitted or Sampled chronologies.