Enum SelectionError 

pub enum SelectionError {
    NoValidParents,
    InvalidSampleSize {
        min_required: usize,
        provided: usize,
    },
    InvalidFitnessForRoulette,
    RouletteSelectionFailed,
}

Errors that can occur during parent selection.

These errors help diagnose configuration or data issues that prevent successful parent selection for breeding operations.

Variants

NoValidParents

No candidates with fitness values are available for selection.

This occurs when all candidates in the population have None fitness values, meaning no candidates have been evaluated yet.

Solution: Ensure candidates are evaluated before attempting selection.

InvalidSampleSize

Invalid sample size for tournament selection configuration.

Tournament selection requires sample_size >= tournament_size * 2 because it runs two separate tournaments (one for each parent in a breeding pair).

Fields

min_required: usize

provided: usize

InvalidFitnessForRoulette

Roulette selection cannot proceed due to invalid fitness values.

This error occurs when:

• Any candidate has negative fitness (< 0.0)
• All candidates have zero fitness (total fitness = 0.0)

Solutions:

• Ensure all fitness values are non-negative
• Verify that at least some candidates have positive fitness
• Consider fitness normalization if needed
• Switch to tournament selection if fitness scaling is problematic

RouletteSelectionFailed

Internal roulette wheel algorithm failure.

This should not occur under normal conditions and indicates a bug in the roulette selection implementation.

Trait Implementations

impl Debug for SelectionError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for SelectionError

fn fmt(&self, __formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for SelectionError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<SelectionError> for Error

fn from(source: SelectionError) -> Self

Converts to this type from the input type.