/**
 * Deterministic randomness and summary statistics for the System One
 * benchmark (T12495). Every random choice (negative sampling, the owner
 * spot-check sample) goes through a seeded generator so a dataset can be
 * rebuilt byte for byte.
 *
 * @task T12495
 * @epic T12486
 */
/** Default seed: the task number, so an unseeded run is still reproducible. */
export declare const DEFAULT_BENCH_SEED = 12495;
/** A seeded generator of floats in [0, 1). */
export type BenchRandom = () => number;
/**
 * Mulberry32: a small, fast, seeded PRNG (not cryptographic).
 *
 * @param seed - 32-bit seed.
 * @returns A generator of floats in [0, 1).
 */
export declare function createSeededRandom(seed: number): BenchRandom;
/**
 * Fisher–Yates shuffle into a new array.
 *
 * @param items - Items to shuffle.
 * @param random - Seeded generator.
 * @returns A shuffled copy.
 */
export declare function shuffled<T>(items: readonly T[], random: BenchRandom): T[];
/**
 * The `p`-th percentile (nearest-rank) of `values`.
 *
 * @param values - Samples.
 * @param p - Percentile in [0, 100].
 * @returns The percentile, or `null` when there are no samples.
 */
export declare function percentile(values: readonly number[], p: number): number | null;
/** Mean and spread of one metric across repeated runs. */
export interface BenchSpread {
    /** Runs that produced a value. */
    readonly n: number;
    /** Arithmetic mean. */
    readonly mean: number | null;
    /** Sample standard deviation (0 for a single run). */
    readonly stddev: number | null;
    /** Smallest value. */
    readonly min: number | null;
    /** Largest value. */
    readonly max: number | null;
}
/**
 * Mean, sample standard deviation, min and max of the non-null values.
 *
 * @param values - One value per run; `null` means the run produced none.
 * @returns The spread.
 */
export declare function spreadOf(values: readonly (number | null)[]): BenchSpread;
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