Garbage Collection in LOGFLOW*

The LOGFLOW is a distributed Prolog system running on multi-transputer machines and workstation clusters. The engines (Distributed Data Driven Prolog Abstract Machines, 3DPAM) execute the Prolog program parallel with fine-grain execution. Coarse-grain pieces of work are executed by traditional sequential WAM (Warren Abstract) machines. In the execution of logic programming languages the memory consumption speed is very high because of a storage cell of the memory cannot be reused when it is filled once. The memory is fulfilled very shortly but most of the allocated storage cells are 'garbage' i.e., they are not used by the system. The 3DPAM engine does not use any space reclamation technique. Our goal is to select an appropriate garbage collection method for it to support the execution of larger programs. In order to find an efficient one an analysis of the system is presented in this paper. After the analysis some algorithm is described and the most appropriate one is suggested for implementation. This paper is the continuation of the paper [2], which gives an overview of the existing garbage collection methods. In Section 2. the data structures of the 3DPAM are described briefly. In section 3. the system is analysed. It describes how the program structures are created in the memory and how they will be garbage. The Section 4. describes collection methods. The conclusion suggests the appropriate methods for both implementations of the LOGFLOW system.