Principles of the DelPhi parallel inference machine

1989

Thus the extended and-or tree has two new nodes: a 'sequential' node (for RAP's sequential goals), and a 'cross-product' node (for the cross-product of solutions from and-or-parallel goals). The other main features of our approach are: (i) each processor's binding-array is accompanied by a base-array, for constant access-t ime to variables in the presence of andparallelism; (ii) coarse-grain parallelism is supported by our processor scheduling poli.q, to minimize the cost of binding-array updates during task-switching; (iii) essentially, two new classes of WAM instructions are introduced: the 'check' instructions of RAP-WA:VI, and 'allocate' instructions for the different types of nodes. (iv) Several optimizations are proposed to minimize the cost of task switrhing. This extended \\"AM is currently being implemented on a Balance Sequent 8000.

Journal of Systems Architecture, 1997

A static model for the parallel execution of logic programs on MIMD distributed memory systems is presented where a refutation is implemented through a process network returned by the compilation of the logic program. The model supports Restricted-AND, OR and stream parallelism and it is integrated with a set of static analyses to optimise the process network. Altogether, the processes interact according to a static data driven model with medium grain operators. Data flowing in the network is tagged to distinguish bindings belonging to the same refutation. A scheduling strategy to integrate low level scheduling and message flow control has been defined. Performance figures are presented.

Information Processing Letters, 1994

An efficient backward execution method for AND-parallelism in logic programs is proposed. It is devised through a close examination of some relation over literals, which can be represented by paths in the data dependency graphs. The scheme is more efficient than other works in the sense that it performs less unfruitful resetting (and consequently, canceling) operations. Its rationale is also intuitively clear and natural. Furthermore, the relevant analyses needed for the proposal are largely achieved at compile time, which alludes to actual efficiency.

Lecture Notes in Computer Science, 1998

Abstract One of the advantages of logic programming (LP) and constraint logic programming (CLP) is the fact that one can exploit implicit parallelism in logic programs. Logic programs have two major forms of implicit parallelism: orparallelism (ORP) and and-parallelism (ANDP). In this work we survey some of work that has been taking place within the C LoPn project towards fast execution of logic programs.

University of Oregon, 1994

CiteSeerX - Document Details (Isaac Councill, Lee Giles): Two major problems that arise in parallel logic programming systems are: (i) redundant computation during and-parallel execution of dependent goals, and, (ii) efficient representation of multiple environments at runtime. Both ...

Parallel Computing, 1999

The OASys (Or/And SYStem) is a software implementation designed for AND/OR-parallel execution of logic programs. In order to combine these two types of parallelism, OASys considers each alternative path as a totally independent computation (leading to OR-parallelism) which consists of a conjunction of determinate subgoals (leading to AND-parallelism). This computation model is motivated by the need for the elimination of communication between processing elements (PEs). OASys aims towards a distributed memory architecture in which the PEs performing the OR-parallel computation possess their own address space while other simple processing units are assigned with AND-parallel computation and share the same address space. OASys execution is based on distributed scheduling which allows either recomputation of paths or environment copying. We discuss in detail the OASys execution scheme and we demonstrate OASys eectiveness by presenting the results obtained by a prototype implementation, running on a network of workstations. The results show that speedup obtained by AND/OR-parallelism is greater than the speedups obtained by exploiting AND or OR-parallelism alone. In addition, comparative performance measurements show that copying has a minor advantage over recomputation. Ó 1999 Elsevier Science B.V. All rights reserved.

2000

One of the advantages of logic programming is the fact that it offers many sources of implicit parallelism, such as and-parallelism and or-parallelism. Arguably, or-parallel systems, such as Aurora and Muse, have been the most successful parallel logic programming systems so far. Or-parallel systems rely on techniques such as Environment Copying to address the problem that branches being explored in parallel may need to assign different bindings for the same shared variable.

1983

Ab.traet DADO is a highly-parallel. VLSI-baaed. tree-~tructured machine d~igned to provide ~ignificant. performance improvements in the execution or large production 8S18tem programs. In tru, paper. we describe clll'nnL research aimed at. implementing PROLOG within the parallel rramework which DADO provid~. The implementation allo .. ~ parallel ~atisraction or both disjunct.ions and conjunctions which occur in the goal tree generated during the execution or a PROLOG program. Local unification routin~ in ea.ch proceS!Of allow parallel satisfaction or disjunctive goals while a parallel relational join operation provid~ a framework to solve conjunctive subgoals. An overview of the techniqu~ currently being implemented and their relationship to the architecture is pr~ented.

Lecture Notes in Computer Science, 2014

Since their popularity began to rise in the mid-2000s there has been significant growth in the number of multi-core and multi-processor computers available. Knowledge representation systems using logical inference have been slow to embrace this new technology. We present the concept of inference graphs, a natural deduction inference system which scales well on multi-core and multiprocessor machines. Inference graphs enhance propositional graphs by treating propositional nodes as tasks which can be scheduled to operate upon messages sent between nodes via the arcs that already exist as part of the propositional graph representation. The use of scheduling heuristics within a prioritized message passing architecture allows inference graphs to perform very well in forward, backward, bi-directional, and focused reasoning. Tests demonstrate the usefulness of our scheduling heuristics, and show significant speedup in both best case and worst case inference scenarios as the number of processors increases.