/**
 * Test-only reference oracle for mutual reachability. Production HDBSCAN
 * computes this on-tensor via a broadcast `tf.maximum` inside
 * `clustering/hdbscan.ts`; this pure-JS version exists so tests can
 * cross-check that path against a simple, readable formula.
 *
 * The mutual-reachability distance smooths raw distance by each point's core
 * (k-)distance:
 *
 *   d_mreach(i, j) = max(core_distance_i, core_distance_j, distance_i_j)
 *
 * Connecting points by mutual reachability rather than raw distance is what
 * makes HDBSCAN robust to single-linkage chaining through sparse regions: a
 * point in a sparse region has a large core distance, so edges through it are
 * inflated and it is harder for it to bridge dense clusters.
 */
/**
 * Diagonal is `core_i` since `distance[i][i] = 0`, giving `max(core_i, core_i, 0) = core_i`.
 * @throws If the dimensions of `distance_matrix` and `core_distances` disagree.
 */
export declare function mutual_reachability(distance_matrix: number[][], core_distances: ArrayLike<number>): number[][];
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