solution_level_control

Cost estimates associated with a set of solution control values.

Specification

• Alias: None

• Arguments: STRING

• Default: use of single default solution level

Description

Simulation-based models may have an associated solution_level_control, which identifies a hierarchy of solution states, such as a set of mesh discretizations from coarse to fine, a set of solver tolerances from loose to tight, etc. The string specified as the solution_level_control identifies a discrete variable label that parameterizes the hierarchy of solution states.

Note: If the discrete variable identified is a discrete set variable, then it is important to note that the variable’s set values will be ordered (lexicographically in the case of string variables), and the ordering of values provided in solution_level_cost should correspond to this set ordering. A common error is to provide a listing of set values that is out of order and then providing a set of costs corresponding to this misordered list – in this case, the solution level costs will be associated with the re-ordered set values.

Examples

In this example, integer solution control values and solution costs are naturally well ordered.

model,
 simulation
   solution_level_control = 'mesh_size'
   solution_level_cost = 1. 8. 64. 512. 4096.

variables,
 uniform_uncertain = 9
   lower_bounds      =  9*-1.
   upper_bounds      =  9* 1.
 discrete_state_set
   integer = 1
         set_values = 4 8 16 32 64
         descriptors = 'mesh_size'

In this example, string solution control values are lexicographically ordered, and care must be taken to align the solution cost estimates.

model,
 simulation
   solution_level_control = 'mesh_size'
   solution_level_cost = 1. 64. 8. # match set ordering

variables,
 uniform_uncertain = 9
   lower_bounds      =  9*-1.
   upper_bounds      =  9* 1.
 discrete_state_set
   string = 1
         set_values = 'COARSE' 'FINE' 'MEDIUM' # lexicographical ordering
         descriptors = 'mesh_size'