miesmuschel (version 0.0.4-3)

mies_get_fitnesses: Get Fitness Values from OptimInstance

Description

Get fitness values in the correct form as used by Selector operators from an OptimInstance. This works for both single-criterion and multi-criterion optimization, and entails multiplying objectives with -1 if they are being minimized, since Selector tries to maximize fitness.

Usage

mies_get_fitnesses(inst, rows)

Value

numeric

matrix with length(rows) (if rows is given, otherwise nrow(inst$archive$data)) rows and one column for each objective: fitnesses to be maximized.

Arguments

inst

(OptimInstance)
Optimization instance to evaluate.

rows

optional (integer)
Indices of rows within inst to consider. If this is not given, then the entire archive is used.

See Also

Other mies building blocks: mies_evaluate_offspring(), mies_generate_offspring(), mies_init_population(), mies_select_from_archive(), mies_step_fidelity(), mies_survival_comma(), mies_survival_plus()

Examples

set.seed(1)
library("bbotk")
lgr::threshold("warn")

# Define the objective to optimize
objective <- ObjectiveRFun$new(
  fun = function(xs) {
    z <- exp(-xs$x^2 - xs$y^2) + 2 * exp(-(2 - xs$x)^2 - (2 - xs$y)^2)
    list(Obj = z)
  },
  domain = ps(x = p_dbl(-2, 4), y = p_dbl(-2, 4)),
  codomain = ps(Obj = p_dbl(tags = "maximize"))
)

# Get a new OptimInstance
oi <- OptimInstanceSingleCrit$new(objective,
  terminator = trm("evals", n_evals = 100)
)

mies_init_population(inst = oi, mu = 3)

oi$archive

mies_get_fitnesses(oi, c(2, 3))

###
# Multi-objective, and automatic maximization:
objective2 <- ObjectiveRFun$new(
  fun = function(xs) list(Obj1 = xs$x^2, Obj2 = -xs$y^2),
  domain = ps(x = p_dbl(-2, 4), y = p_dbl(-2, 4)),
  codomain = ps(
    Obj1 = p_dbl(tags = "minimize"),
    Obj2 = p_dbl(tags = "maximize")
  )
)
# Using MultiCrit!
oi <- OptimInstanceMultiCrit$new(objective2,
  terminator = trm("evals", n_evals = 100)
)

mies_init_population(inst = oi, mu = 3)

oi$archive

# Note Obj1 has a different sign than in the archive.
mies_get_fitnesses(oi, c(2, 3))