In this paper, the performance gain obtained by combining parallel peri- odic real-time processes is elaborated. In certain single-core mono-processor configurations, for example, embedded control systems in robotics comprising many short processes, process context switches may consume a considerable amount of the available processing power. For this reason, it can be advantageous to combine processes, to reduce the number of context switches and thereby increase the performance of the application. As we consider robotic applications only, often consisting of processes with identical periods, release times and deadlines, we restrict these configurations to periodic real-time processes executing on a single-core mono-processor. By graph-theoretical concepts and means, we provide necessary and sufficient conditions so that the number of context switches can be reduced by combining synchronising processes.
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Reading and writing is modelled in CSP using actions containing the symbols ? and !. These reading actions and writing actions are synchronous, and there is a one-to-one relationship between occurrences of pairs of these actions. In the CPA conference 2017, we introduced the extended half-synchronous al- phabetised parallel operator X ⇕ Y , which disconnects the writing to and reading from a channel in time; the reading processes are divided into sets which are set-wise asynchronous, but intra-set-wise synchronous, giving full flexibility to the reads. In this paper, we allow multiple writers to write to the same channel set-wise asynchronously, but intra-set-wise synchronously and we study the impact on our (Extended) Vertex Removing Synchronised Product. The advantages we accomplish are that the extension of X ⇕ Y gives more flexibility by indexing the writing actions and the reading actions, leading to a straightforward majority vote design. Furthermore, the extension of X ⇕ Y preserves the advantages of the X ⇕ Y operator.
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Reading and writing is modelled in CSP using actions containing the symbols ? and !. These reading actions and writing actions are synchronous, and there is a one-to-one relationship between occurrences of pairs of these actions. In the CPA conference 2016, we introduced the half-synchronous alphabetised parallel operator X ⇓ Y , which disconnects the writing to and reading from a channel in time. We introduce in this paper an extension of X ⇓ Y , where the definition of X ⇓ Y is relaxed; the reading processes are divided into sets which are set-wise asynchronous, but intra-set-wise synchronous, giving full flexibility to the asynchronous writes and reads. Furthermore, we allow multiple writers to the same channel and we study the impact on a Vertex Removing Synchronised Product. The advantages we accomplish are that the extension of X ⇓ Y gives more flexibility by indexing the reading actions and allowing multiple write actions to the same channel. Furthermore, the extension of X ⇓Y reduces the end-to-end processing time of the processor or coprocessor in a distributed computing system. We show the effects of these advantages in a case study describing a Controlled Emergency Stop for a processor-coprocessor combination.
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