Efficient Management of Backtracking in AND-Parallelism

A b a c k t r a c k i n g a lgor i thm for AND-Para l l e l i sm and its imp lemen ta t i on at the Abstract Mach ine level are presen ted : first, a class of AND-Para l l e l i sm models based on goal independence is defined, and a generalized version of Res t r ic ted AND-Para l l e l i sm ( R A P ) in t roduced as cha rac te r i s t i c of th is class. A s imple and efficient b a c k t r a c k i n g algor i thm for R A P is then discussed. An imp lemen ta t i on scheme is presented for th is a lgor i thm which offers m i n i m u m overhead , while re ta in ing the per formance and s torage economy of sequent ial i m p l e m e n t a t i o n s and t ak ing a d v a n t a g e of goal independence to avoid unnecessary b a c k t r a c k i n g ( " res t r i c t ed intel l igent b a c k t r a c k i n g " ) . Final ly, the implementa t ion of b a c k t r a c k i n g in sequent ia l and AND-Para l l c l sys t ems is explained through a number of examples .