The author considers the design of control programs for systems with many degrees of freedom and multiple goals. These systems have several features requiring nontraditional control techniques. The author proposes a f...
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ISBN:
(纸本)0818689870
The author considers the design of control programs for systems with many degrees of freedom and multiple goals. These systems have several features requiring nontraditional control techniques. The author proposes a framework for the control of such systems. In this framework, it is possible to create abstract domains of interest and relate them to sensed and actuated quantities. Motions are programmed by specifying inequality or equality constraints in these domains, possibly changing over time, which have to be satisfied in order to achieve the task. A trajectory satisfying the constraints is picked at run time. The framework has a number of benefits, including the ability to deal with redundancy and the partial specification of motion;the ability to divide the control task into independent, concurrent modules which can be separately developed and debugged;the possibility of parallel execution;ease of modification of existing programs;and the ability to handle multiple sensors and actuators in a uniform fashion. An experimental version of this framework has been implemented with encouraging results.
An unsupervised paralleldistributed adaptive controller for nonlinear systems is proposed. It is shown to provide bounded tracking and asymptotic regulation following an arbitrary 'teacher'. A two-degrees-of-...
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An unsupervised paralleldistributed adaptive controller for nonlinear systems is proposed. It is shown to provide bounded tracking and asymptotic regulation following an arbitrary 'teacher'. A two-degrees-of-freedom robotic simulation example is provided, which demonstrates the feasibility of the proposed method.< >
Several effective algorithms are presented for the optimal allocation of computer resources in a proposed stream-oriented parallel-processing scheme for database operations. These algorithms can be utilized to obtain ...
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Several effective algorithms are presented for the optimal allocation of computer resources in a proposed stream-oriented parallel-processing scheme for database operations. These algorithms can be utilized to obtain the optimal allocation of memory resources for every type of query in sequential-processing environments, parallel-processing environments with shared-memory multiprocessors, and distributed-processing environments. The computation complexities of the proposed algorithms are analyzed and used to clarify the effectiveness of those algorithms.< >
Four distributed query processing strategies under consideration for incorporation into the Cronus object-oriented distributed computing environment are described. Under Cronus, object storage can be embedded inside a...
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Four distributed query processing strategies under consideration for incorporation into the Cronus object-oriented distributed computing environment are described. Under Cronus, object storage can be embedded inside applications, and facilities are provided to distribute and replicate automatically the data maintained by the application. The performance of the query processing strategies is analyzed within this environment. The resulting evaluation points out the factors to consider in developing query processing strategies for replicated, object-oriented data, and the impact of those factors on the cost and optimality of the strategies. The evaluation led to the adoption of an optimistic, decentralized strategy which increases parallelism and decreases the size of messages at the expense of an increase in the number of messages transferred.< >
The author considers the design of control programs for systems with many degrees of freedom and multiple goals. These systems have several features requiring nontraditional control techniques. The author proposes a f...
详细信息
The author considers the design of control programs for systems with many degrees of freedom and multiple goals. These systems have several features requiring nontraditional control techniques. The author proposes a framework for the control of such systems. In this framework, it is possible to create abstract domains of interest and relate them to sensed and actuated quantities. Motions are programmed by specifying inequality or equality constraints in these domains, possibly changing over time, which have to be satisfied in order to achieve the task. A trajectory satisfying the constraints is picked at run time. The framework has a number of benefits, including the ability to deal with redundancy and the partial specification of motion; the ability to divide the control task into independent, concurrent modules which can be separately developed and debugged; the possibility of parallel execution; ease of modification of existing programs; and the ability to handle multiple sensors and actuators in a uniform fashion. An experimental version of this framework has been implemented with encouraging results.< >
A recovery procedure for distributedsystems using the time warp control mechanism is described. Time warp is an optimistic execution technique in which synchronization is achieved using rollback. The recovery procedu...
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A recovery procedure for distributedsystems using the time warp control mechanism is described. Time warp is an optimistic execution technique in which synchronization is achieved using rollback. The recovery procedure is a protocol that exploits the redundancy already available to implement process rollback in the time warp mechanism. Thus, the recovery protocol has little additional bookkeeping overhead, unlike many other recovery procedures. An informal proof of the correctness of the recovery procedure for a single process failure is presented. The protocol is extended so that it becomes resilient to multiple process failures.< >
The multiprocessor Sequent Symmetry was first delivered to customers with write-through caches. Later on each machine was upgraded with copy-back caches. Because all the other architectural parameters were unchanged (...
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The multiprocessor Sequent Symmetry was first delivered to customers with write-through caches. Later on each machine was upgraded with copy-back caches. Because all the other architectural parameters were unchanged (main memory, bus, cache organization and size, and so on), this made it possible to measure the performance of a multiprocessor with no caches, write-through caches, and copy-back caches. We also study the impact that the language (FORTRAN and C) has on the performance of the machine.
作者:
C. LiebeltIPVR
Institute of Parallel and Distributed Super-Computers University of Stuttgart Stuttgart Germany
Transaction programs by definition have to maintain all consistency constraints defined on a database. Although the overall operational consistency of a database rests on this crucial assumption, there are few design ...
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Transaction programs by definition have to maintain all consistency constraints defined on a database. Although the overall operational consistency of a database rests on this crucial assumption, there are few design aids to support the design of consistent transaction programs. An approach is presented for verifying that the defined integrity constraints are not violated by a transaction program. Assuming that the database is in a consistent state before the transaction program starts, the database stays consistent after the execution of a correct transaction program. In this approach all computations and all modifications on the database are identified and represented with symbolic values. The symbolic representation of the output variables and database operations is used to verify the integrity constraints. Therefore, it is possible to support the application programmer in designing correct transaction programs.< >
The authors explore the notion of node autonomy in distributed computer systems. Some motivations for autonomy are presented. Different facets of autonomy as well as relationships among them are discussed. Finally, th...
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ISBN:
(纸本)0818608935
The authors explore the notion of node autonomy in distributed computer systems. Some motivations for autonomy are presented. Different facets of autonomy as well as relationships among them are discussed. Finally, they examine how autonomy affects other aspects of distributed computing, including timeliness, correctness, load sharing, data sharing, and data replication.
The author describes the state of the art in models of concurrency. The models are analyzed along two dimensions: communication and computation. Some problems which make it difficult to realize large-scale concurrent ...
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ISBN:
(纸本)0818608935
The author describes the state of the art in models of concurrency. The models are analyzed along two dimensions: communication and computation. Some problems which make it difficult to realize large-scale concurrent systems are examined. Such problems include compositionality, heterogeneity, debugging, resource management, and concurrency control. Some useful comparisons are drawn to problems in distributeddatabases, and it is argued that solutions to these problems cross disciplinary boundaries. Finally, the author discusses trends in building concurrent computers and provides some expectations for the future.
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