Search performance of double-linked coalesced hashing can not exceed “bucketing”

Abstract

Coalesced hashing is an efficient class of hashing technique of which the double-linked coalesced hashing technique uses double links instead of single links and it is faster than the existing coalesced hashing algorithms such as early-insertion standard coalesced hashing (EISCH), late-insertion standard coalesced hashing (LISCH), early-insertion coalesced hashing (EICH), late-insertion coalesced hashing (LICH) and varied-insertion coalesced hashing (VICH). This paper describes and analyzes the double-linked standard coalesced hashing (DSCH) and double-linked coalesced hashing (DCH) algorithms. In Algorithm A, the number of probes per successful search in the full table is 7.4% better with double-linked insertion standard coalesced hashing (DISCH) than with LISCH. The number of probes per unsuccessful search in the full table is 28.5% better with DISCH than with LISCH. We also found that the DICH is same or better than EICH, LICH and VICH for all values of load factor for unsuccessful search. DICH is better than EICH, LICH and VICH for address factor ⩾ 0.9 for successful searches. In Algorithm B, there is no separate cellar but every slot may be used as a cellar (if empty) and the performance is shown to be same as Bucket Chaining.