kgal-core/kgal.statistics/StatisticsConfigScope/guaranteedSorted

guaranteedSorted

open override var guaranteedSorted: Boolean

Optimization flag for statistics. Default is false.

NOTE:

it is not recommended to use this optimization for cGA
use it if you expect performance gains for statistical operators when getting a sorted population, see example below

If true:

executes Best, Worst, Mean with O(1)
statistics operators change their implementation - waiting to receive a sorted population in descending order only
executes it only in safe zones of evolve strategy (see Example below)

If false:

executes Best, Worst with O(N), Mean with O(N*log(N)).
order in population is irrelevant

Example:

statisticsConfig {
    guaranteedSorted = true // Set flag to true
}

// create evolution strategy
evolve {
    // other genetic operators
    // Danger zone: the order of chromosomes is unknown
    evaluation(sortAfter = true) // evaluate population and sort in descending order
    // Safe zone: population sorted by descending
    stat(best(), worst()) // OK but inefficient:
    // without sorting: O(N) + O(N)
    // with sorting: O(N*log(N)) + O(1) + O(1)

    // other genetic operators
    // Danger zone: the order of chromosomes is unknown
    population.sort()
    // Safe zone: population sorted by descending
    stat(best(), mean(), worst()) // OK and efficient
    // without sorting: O(N) + O(N*log(N)) + O(N)
    // with sorting: O(N*log(N)) + O(1) + O(1)
}

guaranteedSorted

See also