Actual search time benchmarks obtained searching the entire ChemDB database, with about 5M compounds using a 2.4MHz AMD Opteron processor with 2 GB of memory. Searches are carried using Tanimoto similarity measure with threshold (t = 0.9), or top ten (K = 10), or both. Search times for single-molecule query are expressed in seconds and are averaged over each dataset. The datasets correspond to the six Stahl and Rarey14 datasets, a random set of 1,000 queries extracted from the set of actual ChemDB queries, and a random set of 100 queries taken from the ChemDB. The fraction of the database that needs to be searched is given by 1 — f.