| 1. |
- Ali, Khayri Mohammed, et al.
(författare)
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Global garbage collection for distributed heap storage systems
- 1987. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We present a garbage-collection algorithm, suitable for loosely-coupled multiprocessor systems, in which the processing elements (PE's) share only the communication medium. The algorithm is global, i.e. it involves all the PE's in the system. It allows space compaction, and it uses a system-wide marking phase to mark all accessible objects where a combination of parallel breadth-first/depth-first strategies is used for tracing the object-graphs according to a decentralized credit mechanism that regulates the number of garbage collection messages in the system. The credit mechanism is crucial for determining the space requirement of the garbage-collection messages. Also a variation of the above algorithm is presented for systems with high locality of reference. It allows each PE to perform first its local garbage collection and only invokes the global garbage collection when the freed space by the local collector is insufficient.
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| 2. |
- Appleby, Karen, et al.
(författare)
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Garbage Collection for Prolog Based on WAM (Revised version)
- 1986. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Warren Abstract Machine (WAM) has become a generally accepted standard Prolog implementation technique. Garbage collection is an important aspect in the implementation of any Prolog system. We first present a synopsis of the WAM and then show marking and compaction algorithms that take advantage of WAM's unique use of the data areas. Marking and compaction are performed on both the heap and the trail. The marking and compaction algorithms use pointer reversal techniques, which obviate the need for extra stack space. However, two bits for every pointer on the heap are reserved for the garbage collection algorithm. The algorithm can work on segments of the heap, which may lead to a significant reduction of the total garbage collection time. The time of the algorithms are linear in the size of the areas.
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| 3. |
- Hagersten, Erik, et al.
(författare)
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The cache coherence protocol of the data diffusion machine
- 1989. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Data Diffusion Machine (DDM) is a scalable shared memory multiprocessor in which the location of a datum in the machine is completely decoupled from its address. A data access "snooping" protocol provides an automatic duplication and migration of the data to wherever needed. The protocol also handles data coherence and replacement. The hardware organization consists of a hierarchy of buses and data controllers linking an arbitrary number of processors each having a large set-associative memory. Each data controller has a set-associative directory containing status bits for data under its control. The rest of the system appears to one processor like shared memory system, which makes the DDM a general architecture. The DDM is scalable in that there may be any number of levels in the hierarchy. The logical topmost bus (or any other bus) can be implemented by an unlimited number of physical buses removing an anticipated bottleneck.
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| 4. |
- Hausman, Bogumil, et al.
(författare)
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OR-parallel Prolog made efficient on shared memory multiprocessors
- 1987. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- With the arrival of commercially available shared-memory multiprocessors, Prolog implementation efforts begin to shift from single processor architectures to the new ones. Among the main problems are efficient implementation of operations on variables and of task switching. Most of the solutions proposed so far suffer from expensive, non-constant time implementation of operations on variables. We propose a model (Versions-Vector Model) in which operations on all variables are constant time operations. The price we pay is a non-constant time of a task switch. As a remedy we propose two ways of decreasing that price. The first is promotion of variables on a task switch, from versions-vectors to the stack or heap, making subsequent task switches cheaper. The second is delayed installation of variables in versions-vectors, decreasing the cost of short branches. We believe that the increased memory consumption induced by our model can be accepted as it is traded for speed.
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| 5. |
- Lusk, Ewing, et al.
(författare)
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The Aurora Or-Parallel Prolog system
- 1989. - 2
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Aurora is a prototype or-parallel implementation of the full Prolog language for shared-memory multiprocessors, developed as part of an informal research collaboration known as the "Gigalips Project". It currently runs on Sequent and Encore machines. It has been constructed by adapting Sicstus Prolog, a fast, portable, sequential Prolog system. The techniques for constructing a portable multiprocessor version follow those pioneered in a predecessor system, ANL-WAM. The SRI model was adopted as the means to extend the Sicstus Prolog engine for or-parallel operation. We describe the design and main implementation features of the current Aurora system, and present some experimental results. For a range of benchmarks, Aurora on a 20-processor Sequent Symmetry is 4 to 7 times faster than Quintus Prolog on a Sun 3/75. Good performance is also reported on some large-scale Prolog applications.
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| 6. |
- Sahlin, Dan, et al.
(författare)
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An Intuitionistic Predicate Logic Theorem Prover
- 1989. - 1
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Rapport (refereegranskat)abstract
- A complete theorem prover for intuitionistic predicate logic based on the cut-free calculus is presented. It includes a treatment of "quasi-free" identity based on a delay mechanism and a special form of unification. Several important optimizations of the basic algorithm are introduced. The resulting system is available in source form from SICS; an Appendix gives some idea of its performance.
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