In this paper an optimal algorithm for scheduling requests on interleaved memories is presented. With this algorithm the average completion time for servicing a finite set of randomly generated requests is proved to b...
详细信息
In this paper an optimal algorithm for scheduling requests on interleaved memories is presented. With this algorithm the average completion time for servicing a finite set of randomly generated requests is proved to be minimum. Performance of this algorithm for nonrandom requests has not been proved. However, it is compared with alternate algorithms using simulations. A pipelined processor is used as an example for the generation of nonrandom requests to the memories. Nonetheless, the source could have been a vector processor or a multiprocessor system. Two alternative organizations are investigated, one with a common set of fixed size buffers to store conflicting requests and one with individual fixed size buffers for each module. These two organizations are shown to be equivalent as far as the average utilization and waiting cycles are concerned. An intelligent scheduler determines the order of initiation of the memory modules. An alternative design with separate instruction and data modules is investigated. It is found that separation gains very little in performance because of the unequal rates of access to the instruction and the data modules. The basic assumptions for the analysis are that the dependency effects are ignored and the request rate is very high so that any empty buffers can be filled immediately. The degradation in memory utilization due to dependency effects is studied in a separate paper in this ❉.
The design of a database is a complex and dynamic process that demands comprehensive knowledge and expertise. An interactive database design tool called Gambit is described that supports the entire process in an optim...
详细信息
The design of a database is a complex and dynamic process that demands comprehensive knowledge and expertise. An interactive database design tool called Gambit is described that supports the entire process in an optimal fashion. It is based on an extended relational-entity relationship model, in which the designer receives assistance in outlining and describing data structures. The database programming language Modula/R, which is based on first-order predicate calculus, is used to formulate the constraints; the update transactions are generated automatically as Modula/R programs and encompass all defined integrity constraints. They are gathered in data modules that represent the only interface to the database besides read operations. Gambit has a prototype facility that permits the designer to test the design of the database. The results can be employed as feedback leading to an improvement of the conceptual schema and the transactions.
暂无评论