C. Codognet and P. Codognet. Non-deterministic stream AND-Parallelism based on intelligent backtracking. In Levi and Martelli [13], pages 63-79.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....in Prolog (see [4, 6] is to locate the bindings responsible for the occurrence of a failure, and backtrack directly to their originator, designated as the culprit, so that unnecessary work (i.e. irrelevant to the con ict) is eschewed. To do so, schemes to implement IB in Prolog (for example see [4, 12, 5, 7]) always refer to the Prolog runtime data structures used to implement nondeterminism, namely choice points; i.e. a binding is said to depend on a given goal if it is associated with that goal s choice point. AKL provides no such concept, nondeterminism being handled di erently, by the use of ....

C. Codognet and P. Codognet. Non-deterministic stream AND-Parallelism based on intelligent backtracking. In Levi and Martelli [13], pages 63-79.

....and thus to determine the context in which an agent operates. We believe this can be achieved efficiently by using data dependency tracking techniques as proposed in logic by so called intelligent backtracking techniques [46] or in AI by ATMS [115] and ideas from concurrent logic programming [42]. Investigating the relations and combination of these techniques is a very interesting topic We plan to first investigate the extension of cc(FD) a cc language over finite domains, with abductive features. An abductive cc language offers many advantages for combinatorial problemsolving. The ....

....Limitations of the initial design are now well understood and work is in progress to overcome them. Experience with other constraint systems is also discussed in [87] The work on incrementality can build upon the research on intelligent backtracking both in the sequential and concurrent cases [44, 42, 46]. Preliminary results on assumption based constraint languages are reported in [151] Linear constraint solving over numeric domains has been investigated in various CLP systems such as PROLOG III [140] CLP(R) 106] CHIP [84] etc. Linear constraints simplification is mainly based on the method ....

C. Codognet and P. Codognet. Non-deterministic stream and-parallelism based on intelligent backtracking. In Proceedings of the 6th International Conference on Logic Programming. MIT Press, 1991.

....: Z = X append(Xs; Y s; Zs) true: Prolog notation is allowed in Babel as a syntactic sugar of the functional definition. 3 Exploiting And parallelism Several sources of parallelism for Babel can be considered: independent And parallelism [8, 11] Or parallelism [24] Stream parallelism [6], and Unification parallelism [7] for logic programming. Independent And parallelism consists of the parallel execution of independent goals in a clause. Or parallelism consists of the parallel execution of clauses in a procedure. Stream parallelism exploits the parallelism of goals that share ....

C. Codognet and Philippe Codognet. Non-deterministic Stream AND-Parallelism based on intelligent backtracking. Proceedings of the International Conference of Fifth Generation Computer Systems, ICOT, 1984.

....tree has to be explicitly represented. One important aspect of our work is that the information we use for the backward execution is very limited and the goal of this work is not to attempt anything like intelligent backtracking as has been proposed for Prolog [1, 3, 4] or concurrent languages [2]. Intelligent backtracking would require using data dependency information in some way. This requires to record more information, usually during the unification process, in order to determine dependencies between failing goals and choice points, based on data dependencies. We preferred to ....

....when compared to Prolog, but failure information on backward execution can further improve this. A priori pruning should be combined with a posteriori pruning. ffl Some of the non deterministic examples were adapted 2 from similar ones used for benchmarking intelligent backtracking methods[4, 2]. They do not benefit as much from this type of manipulation as we initially expected; this is due to the fact that the Andorra principle already improves the naive version. A striking example of this is the color 13 program. A good order of goals in the query gives the solution immediately and ....

C. Codognet and P. Codognet. Non-deterministic stream AND-Parallelism based on intelligent backtracking. In Levi and Martelli [17], pages 63--79.

....to try an alternative choice rather than relaxing extra constraints. As in intelligent backtracking methods, an alternative set is associated to each disjunction cf. the Alt sets of [4] and disjunctions to be re inserted are restarted from the first alternative cf. the selective reset of [3]. The use of disjunctive constraints is very useful for the final generation of solutions. After the pruning due to all constraints being treated, some variables may still have several possible values in their domains. If the domain of a variable v is fw 1 ; wng then adding a constraint ....

C. Codognet and P. Codognet. Non-deterministic Stream AND-Parallelism based on Intelligent Backtracking. In Proceedings of 6th ICLP, Lisbon, 1989. The MIT press.

....like AC [10] AC 4 [11] and AC 5 [17] for finite domains, or unification over first order terms are instances of such local solvers. Up to now, the deletion of unification constraints in Prolog like systems has been tackled by so called selective reset in extended intelligent backtracking methods [3, 7]. However, even if such methods can be extended to finite domain constraints [5, 14] they rely on complex dependency recording mechanisms that amount to runtime overhead, even if no deletion is later used. Instead, we would like to take advantage of the dependency information already present in ....

C. Codognet and P. Codognet. Non-deterministic Stream AND-Parallelism based on Intelligent Backtracking. In Proceedings of 6th ICLP, Lisbon, 1989. The MIT Press.

....are propagation techniques (e.g. AC [19] AC 4 [20] AC 5 [28] for finite domains, or unification over first order terms. Up to now, the deletion of unification constraints in Prolog like systems has been tackled by so called selective reset in extended intelligent backtracking methods, see [3] or [13] However, even if such methods can be extended to finite domain constraints [6, 25] they rely on complex dependency recording mechanisms that amount to runtime overhead, even if no deletion is later used. To avoid these problems, our idea is to take advantage of the dependency ....

C. Codognet and P. Codognet. Non-deterministic Stream AND-Parallelism based on Intelligent Backtracking. In Proc. ICLP'89, 6th International Conference on Logic Programming, Lisbon, 1989. The MIT Press.

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