Speed with a quality measure

When mode is approximate, require a current index and a positive efSearch. Navigate greedily from the top-layer entry point, descend through layers, and keep up to efSearch candidates on layer zero. Return the best k plus visited, the number of distinct nodes whose distance you computed.

When efSearch is at least the number of nodes, visit the whole store; this guarantees exact results and makes small cases reproducible. Without mode, search preserves the previous exhaustive behavior.

evaluate receives a list of queries and computes approximate and exact ids for each. Report the average |approximate ∩ exact| / k, rounded to six decimals, and the query count.

• Never query a stale index.
• visited counts unique distance calculations.
• Recall compares ids, not rounded distances.