export interface MergeResult {
    /** The new canonical checkpoint (base + merged delta), ready to repackage. */
    checkpoint: ArrayBuffer;
    /** How many distinct elements the merged delta touches. */
    mergedRows: number;
    /** How many contributor deltas were folded in. */
    contributors: number;
    /** L2 norm of the ACTUAL weight movement base→merged, (Σ(merged−base)²)^½. 0 when nothing moved. */
    deltaNorm: number;
}
/**
 * Fold contributor weight-deltas (each a serialized RowDelta vs the SAME base) into
 * one merged checkpoint by FedAvg-over-contributors.
 *
 * @param baseCheckpoint the canonical checkpoint the deltas were diffed against
 * @param diffs          serialized RowDelta buffers (from `diffCheckpoints`)
 * @param weights        optional per-diff sample weights (default 1 each = plain mean);
 *                       a zero/negative weight excludes that contributor
 */
export declare function mergeCheckpointDiffs(baseCheckpoint: ArrayBuffer, diffs: ArrayBuffer[], weights?: number[]): MergeResult;
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